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  • Mysql query in drupal database - groupwise maximum with duplicate data

    - by nselikoff
    I'm working on a mysql query in a Drupal database that pulls together users and two different cck content types. I know people ask for help with groupwise maximum queries all the time... I've done my best but I need help. This is what I have so far: # the artists SELECT users.uid, users.name AS username, n1.title AS artist_name FROM users LEFT JOIN users_roles ur ON users.uid=ur.uid INNER JOIN role r ON ur.rid=r.rid AND r.name='artist' LEFT JOIN node n1 ON n1.uid = users.uid AND n1.type = 'submission' WHERE users.status = 1 ORDER BY users.name; This gives me data that looks like: uid username artist_name 1 foo Joe the Plumber 2 bar Jane Doe 3 baz The Tooth Fairy Also, I've got this query: # artwork SELECT n.nid, n.uid, a.field_order_value FROM node n LEFT JOIN content_type_artwork a ON n.nid = a.nid WHERE n.type = 'artwork' ORDER BY n.uid, a.field_order_value; Which gives me data like this: nid uid field_order_value 1 1 1 2 1 3 3 1 2 4 2 NULL 5 3 1 6 3 1 Additional relevant info: nid is the primary key for an Artwork every Artist has one or more Artworks valid data for field_order_value is NULL, 1, 2, 3, or 4 field_order_value is not necessarily unique per Artist - an Artist could have 4 Artworks all with field_order_value = 1. What I want is the row with the minimum field_order_value from my second query joined with the artist information from the first query. In cases where the field_order_value is not valuable information (either because the Artist has used duplicate values among their Artworks or left that field NULL), I would like the row with the minimum nid from the second query.

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  • Mysql query taking too much time

    - by aditya
    I have problem related to mysql database. i am linux webserver admin and i am facing a problem with a mysql query. The database is very small. I tried to track in logs and found that a query is taking minimum 5 sec to respond . The first page of site is coming from the database. Client are using cms. when the server gets some number of hits database server starts to give response very slowly and wait time increases from 5 sec to several seconds. I checked slow query logs { Query_time: 11.480138 Lock_time: 0.003837 Rows_sent: 921 Rows_examined: 3333 SET timestamp=1346656767; SELECT `Tender`.`id`, `Tender`.`department_id`, `Tender`.`title_english`, `Tender`.`content_english`, `Tender`.`title_hindi`, `Tender`.`content_hindi`, `Tender`.`file_name`, `Tender`.`start_publish`, `Tender`.`end_publish`, `Tender`.`publish`, `Tender`.`status`, `Tender`.`createdBy`, `Tender`.`created`, `Tender`.`modifyBy`, `Tender`.`modified` FROM `mcms_tenders` AS `Tender` WHERE `Tender`.`department_id` IN ( 31, 33, 32, 30 ); } Every line in the log is same only there is diff in Query time. Is there any way tweak the performance?

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  • mysql select query optimization

    - by Saharsh Shah
    I have two table testa & testb. CREATE TABLE `testa` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `testb` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, `aid1` INT(10) DEFAULT NULL, `aid2` INT(10) DEFAULT NULL, `aid3` INT(10) DEFAULT NULL, PRIMARY KEY (`id`) ); Currently I am running below query for retrieving all rows where id in testa table matches with any columns of aid1,aid2,aid3 in tableb. The query is retreiving acurate result but it is taking minimum 30 seconds to execute which is too much. I have also tried to optimise my query using UNION but failed to do so. SELECT a.id, a.name, b.name, b.id FROM testb b INNER JOIN testa a ON b.aid1 = a.id OR b.aid2 = a.id OR b.aid3 = a.id ; How do i optimize my query so it's total execution time is within 2-3 seconds? Thanks in advance...

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  • How to normalize a database where different user groups have different kinds of profiles?

    - by Stephen
    My application database has a Groups table that separates users into logical roles and defines access levels (admin, owner, salesperson, customer service, etc.) Groups has many Users. The Users table contains login details such as username and password. Now I wish to add user profiles to my database. The trouble I'm having (probably due to my relative unfamiliarity with proper database normalization) is that different user groups have different kinds of profiles. Ergo, a salesperson's profile will include his commission percentage, whereas an admin or customer service would not need this value. So, would the proper method be to create a unique profile table for each group? (e.g. admin_profiles, or salesperson_profiles). or is there a better way that combines certain details in a generic profile, while some users have extended info. And if so, whats a good example of how to do this with the commission example given?

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  • Error using iif in ms access query

    - by naveen
    I am trying to fire this query in MS Access SELECT file_number, IIF(invoice_type='Spent on Coding',SUM(CINT(invoice_amount)), 0) as CodingExpense FROM invoice GROUP BY file_number I am getting this error Error in list of function arguments: '=' not recognized. Unable to parse query text. I tried replacing IIF with SWITCH to no avail. What's wrong with my query and how to correct this?

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  • mysql query not running correctly from inside the application

    - by Mala
    I am completely stumped. Here is my php (CodeIgniter) code: function mod() { $uid = $this->session->userdata('uid'); $pid = $this->input->post('pid'); if ($this->_verify($uid,$pid)) { $name = $this->input->post('name'); $price = $this->input->post('price'); $curr = $this->input->post('curr'); $url = $this->input->post('url'); $query = $this->db->query("UPDATE items SET name=".$this->db->escape($name).", price=".$this->db->escape($price).", currency=".$this->db->escape($curr),", url=".$this->db->escape($url)." WHERE pid=".$this->db->escape($pid)." LIMIT 1"); } header('location: '.$this->session->userdata('current')); } The purpose of this code is to modify the properties (name, price, currency, url) of a row in the 'items' table (priary key is pid). However, for some reason, allowing this function to run once modifies the name, price, currency and url of ALL entries in the table, regardless of their pid and of the LIMIT 1 thing I tacked on the end of the query. It's as if the last line of the query is being completely ignored. As if this wasn't strance enough, I replaced "$query = $this->db->query(" with an "echo" to see the SQL query being run, and it outputs a query much like I would expect: UPDATE items SET name='newname', price='newprice', currency='newcurrency', url='newurl' WHERE pid='10' LIMIT 1 Copy-pasting this into a MySQL window acts exactly as I want: it modifies the row with the selected pid. What is going on here???

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  • php codeigniter MySQL search query

    - by kalafun
    I want to create a search query on MySQL database that will consist of 5 different strings typed in from user. I want to query 5 different table columns with these strings. When I for example have input fields like: first name, last name, address, post number, city. How should I query the database that I dont always get all the rows. My query is something like this: SELECT user_id, username from users where a like %?% AND b like %?% AND c like %?% AND d like %?% AND e like %?%; When I exchange the AND for OR I always get all the results which makes sense, and when I use AND I get only the exact matches... Is there any function or statement that would help me with this?

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  • Problem with mysql query in paging

    - by jasmine
    I have a very simple paging and mysql query. Im not sure that my query is right: $perPage =4; $page= (isset($GET['page']) && is_numeric($GET['page'])) ? $_GET['page'] : 1; $start = ($page * $perPage ) - $perPage ; if (is_numeric($_GET['cID'])){$cid = $_GET['cID'];} $totalCount = sprintf("SELECT COUNT(*) as 'Total' FROM content WHERE catID = %d", $cid ) ; $count = mysql_query($totalCount); $rowCount = mysql_fetch_array($count); $sql = sprintf("SELECT id, title, abstract, content_image FROM content WHERE catID = %d ORDER BY id DESC LIMIT %d, %d", $cid, $start, $perPage ); $query = mysql_query($sql) or die(mysql_error()); while($row = mysql_fetch_array($query)){ echo $row['id'].' : '. $row['title'] .'<br>'; } with /categories.php?cID=1&page=2 and /categories.php?cID=1&page=1 The output is: 95 : titlev 94 : titlex 93 : titlec 92 : titleb and not changed. What is wrong in my query? Thanks in advance

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  • seperated mysql statement query in php

    - by stone
    So, I can run the following statements from within mysql itself successfully. SET @fname = 'point1'; SELECT * FROM country WHERE name=@fname;` But when I try to pass the query through php like this and run it, I get an error on the second line $query = "SET @fname = 'point1';"; $query .= "SELECT * FROM country WHERE name=@fname;";

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  • Help with SQL query

    - by user154301
    Hello, I have list of DateTime values, and for each value I need to fetch something from the database. I would like to do this with one query. I know it's possible to pass a table (list) to the stored procedure, but Im not sure how to write the query itself. Let's say I have the following table: CREATE TABLE Shows( ShowId [int] NOT NULL, StartTime DateTime NOT NULL, EndTime DateTime NOT NULL ) and an array of dates DECLARE @myDateArray MyCustomDateArrayType Now, if I were fetching a single item, I would write a query like this: SELECT * FROM Shows WHERE StartTime > @ArrayItem and @ArrayItem < EndTime where @ArrayItem is an item from @myDateArray . But how do I formulate the query that would fetch the information for all array items? Thanks!

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  • TOTD #166: Using NoSQL database in your Java EE 6 Applications on GlassFish - MongoDB for now!

    - by arungupta
    The Java EE 6 platform includes Java Persistence API to work with RDBMS. The JPA specification defines a comprehensive API that includes, but not restricted to, how a database table can be mapped to a POJO and vice versa, provides mechanisms how a PersistenceContext can be injected in a @Stateless bean and then be used for performing different operations on the database table and write typesafe queries. There are several well known advantages of RDBMS but the NoSQL movement has gained traction over past couple of years. The NoSQL databases are not intended to be a replacement for the mainstream RDBMS. As Philosophy of NoSQL explains, NoSQL database was designed for casual use where all the features typically provided by an RDBMS are not required. The name "NoSQL" is more of a category of databases that is more known for what it is not rather than what it is. The basic principles of NoSQL database are: No need to have a pre-defined schema and that makes them a schema-less database. Addition of new properties to existing objects is easy and does not require ALTER TABLE. The unstructured data gives flexibility to change the format of data any time without downtime or reduced service levels. Also there are no joins happening on the server because there is no structure and thus no relation between them. Scalability and performance is more important than the entire set of functionality typically provided by an RDBMS. This set of databases provide eventual consistency and/or transactions restricted to single items but more focus on CRUD. Not be restricted to SQL to access the information stored in the backing database. Designed to scale-out (horizontal) instead of scale-up (vertical). This is important knowing that databases, and everything else as well, is moving into the cloud. RBDMS can scale-out using sharding but requires complex management and not for the faint of heart. Unlike RBDMS which require a separate caching tier, most of the NoSQL databases comes with integrated caching. Designed for less management and simpler data models lead to lower administration as well. There are primarily three types of NoSQL databases: Key-Value stores (e.g. Cassandra and Riak) Document databases (MongoDB or CouchDB) Graph databases (Neo4J) You may think NoSQL is panacea but as I mentioned above they are not meant to replace the mainstream databases and here is why: RDBMS have been around for many years, very stable, and functionally rich. This is something CIOs and CTOs can bet their money on without much worry. There is a reason 98% of Fortune 100 companies run Oracle :-) NoSQL is cutting edge, brings excitement to developers, but enterprises are cautious about them. Commercial databases like Oracle are well supported by the backing enterprises in terms of providing support resources on a global scale. There is a full ecosystem built around these commercial databases providing training, performance tuning, architecture guidance, and everything else. NoSQL is fairly new and typically backed by a single company not able to meet the scale of these big enterprises. NoSQL databases are good for CRUDing operations but business intelligence is extremely important for enterprises to stay competitive. RDBMS provide extensive tooling to generate this data but that was not the original intention of NoSQL databases and is lacking in that area. Generating any meaningful information other than CRUDing require extensive programming. Not suited for complex transactions such as banking systems or other highly transactional applications requiring 2-phase commit. SQL cannot be used with NoSQL databases and writing simple queries can be involving. Enough talking, lets take a look at some code. This blog has published multiple blogs on how to access a RDBMS using JPA in a Java EE 6 application. This Tip Of The Day (TOTD) will show you can use MongoDB (a document-oriented database) with a typical 3-tier Java EE 6 application. Lets get started! The complete source code of this project can be downloaded here. Download MongoDB for your platform from here (1.8.2 as of this writing) and start the server as: arun@ArunUbuntu:~/tools/mongodb-linux-x86_64-1.8.2/bin$./mongod./mongod --help for help and startup optionsSun Jun 26 20:41:11 [initandlisten] MongoDB starting : pid=11210port=27017 dbpath=/data/db/ 64-bit Sun Jun 26 20:41:11 [initandlisten] db version v1.8.2, pdfile version4.5Sun Jun 26 20:41:11 [initandlisten] git version:433bbaa14aaba6860da15bd4de8edf600f56501bSun Jun 26 20:41:11 [initandlisten] build sys info: Linuxbs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 2017:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41Sun Jun 26 20:41:11 [initandlisten] waiting for connections on port 27017Sun Jun 26 20:41:11 [websvr] web admin interface listening on port 28017 The default directory for the database is /data/db and needs to be created as: sudo mkdir -p /data/db/sudo chown `id -u` /data/db You can specify a different directory using "--dbpath" option. Refer to Quickstart for your specific platform. Using NetBeans, create a Java EE 6 project and make sure to enable CDI and add JavaServer Faces framework. Download MongoDB Java Driver (2.6.3 of this writing) and add it to the project library by selecting "Properties", "LIbraries", "Add Library...", creating a new library by specifying the location of the JAR file, and adding the library to the created project. Edit the generated "index.xhtml" such that it looks like: <h1>Add a new movie</h1><h:form> Name: <h:inputText value="#{movie.name}" size="20"/><br/> Year: <h:inputText value="#{movie.year}" size="6"/><br/> Language: <h:inputText value="#{movie.language}" size="20"/><br/> <h:commandButton actionListener="#{movieSessionBean.createMovie}" action="show" title="Add" value="submit"/></h:form> This page has a simple HTML form with three text boxes and a submit button. The text boxes take name, year, and language of a movie and the submit button invokes the "createMovie" method of "movieSessionBean" and then render "show.xhtml". Create "show.xhtml" ("New" -> "Other..." -> "Other" -> "XHTML File") such that it looks like: <head> <title><h1>List of movies</h1></title> </head> <body> <h:form> <h:dataTable value="#{movieSessionBean.movies}" var="m" > <h:column><f:facet name="header">Name</f:facet>#{m.name}</h:column> <h:column><f:facet name="header">Year</f:facet>#{m.year}</h:column> <h:column><f:facet name="header">Language</f:facet>#{m.language}</h:column> </h:dataTable> </h:form> This page shows the name, year, and language of all movies stored in the database so far. The list of movies is returned by "movieSessionBean.movies" property. Now create the "Movie" class such that it looks like: import com.mongodb.BasicDBObject;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import javax.enterprise.inject.Model;import javax.validation.constraints.Size;/** * @author arun */@Modelpublic class Movie { @Size(min=1, max=20) private String name; @Size(min=1, max=20) private String language; private int year; // getters and setters for "name", "year", "language" public BasicDBObject toDBObject() { BasicDBObject doc = new BasicDBObject(); doc.put("name", name); doc.put("year", year); doc.put("language", language); return doc; } public static Movie fromDBObject(DBObject doc) { Movie m = new Movie(); m.name = (String)doc.get("name"); m.year = (int)doc.get("year"); m.language = (String)doc.get("language"); return m; } @Override public String toString() { return name + ", " + year + ", " + language; }} Other than the usual boilerplate code, the key methods here are "toDBObject" and "fromDBObject". These methods provide a conversion from "Movie" -> "DBObject" and vice versa. The "DBObject" is a MongoDB class that comes as part of the mongo-2.6.3.jar file and which we added to our project earlier.  The complete javadoc for 2.6.3 can be seen here. Notice, this class also uses Bean Validation constraints and will be honored by the JSF layer. Finally, create "MovieSessionBean" stateless EJB with all the business logic such that it looks like: package org.glassfish.samples;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import java.net.UnknownHostException;import java.util.ArrayList;import java.util.List;import javax.annotation.PostConstruct;import javax.ejb.Stateless;import javax.inject.Inject;import javax.inject.Named;/** * @author arun */@Stateless@Namedpublic class MovieSessionBean { @Inject Movie movie; DBCollection movieColl; @PostConstruct private void initDB() throws UnknownHostException { Mongo m = new Mongo(); DB db = m.getDB("movieDB"); movieColl = db.getCollection("movies"); if (movieColl == null) { movieColl = db.createCollection("movies", null); } } public void createMovie() { BasicDBObject doc = movie.toDBObject(); movieColl.insert(doc); } public List<Movie> getMovies() { List<Movie> movies = new ArrayList(); DBCursor cur = movieColl.find(); System.out.println("getMovies: Found " + cur.size() + " movie(s)"); for (DBObject dbo : cur.toArray()) { movies.add(Movie.fromDBObject(dbo)); } return movies; }} The database is initialized in @PostConstruct. Instead of a working with a database table, NoSQL databases work with a schema-less document. The "Movie" class is the document in our case and stored in the collection "movies". The collection allows us to perform query functions on all movies. The "getMovies" method invokes "find" method on the collection which is equivalent to the SQL query "select * from movies" and then returns a List<Movie>. Also notice that there is no "persistence.xml" in the project. Right-click and run the project to see the output as: Enter some values in the text box and click on enter to see the result as: If you reached here then you've successfully used MongoDB in your Java EE 6 application, congratulations! Some food for thought and further play ... SQL to MongoDB mapping shows mapping between traditional SQL -> Mongo query language. Tutorial shows fun things you can do with MongoDB. Try the interactive online shell  The cookbook provides common ways of using MongoDB In terms of this project, here are some tasks that can be tried: Encapsulate database management in a JPA persistence provider. Is it even worth it because the capabilities are going to be very different ? MongoDB uses "BSonObject" class for JSON representation, add @XmlRootElement on a POJO and how a compatible JSON representation can be generated. This will make the fromXXX and toXXX methods redundant.

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  • SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28

    - by pinaldave
    CXPACKET has to be most popular one of all wait stats. I have commonly seen this wait stat as one of the top 5 wait stats in most of the systems with more than one CPU. Books On-Line: Occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if contention on this wait type becomes a problem. CXPACKET Explanation: When a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. There is an organizer/coordinator thread (thread 0), which takes waits for all the threads to complete and gathers result together to present on the client’s side. The organizer thread has to wait for the all the threads to finish before it can move ahead. The Wait by this organizer thread for slow threads to complete is called CXPACKET wait. Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query. Reducing CXPACKET wait: We cannot discuss about reducing the CXPACKET wait without talking about the server workload type. OLTP: On Pure OLTP system, where the transactions are smaller and queries are not long but very quick usually, set the “Maximum Degree of Parallelism” to 1 (one). This way it makes sure that the query never goes for parallelism and does not incur more engine overhead. EXEC sys.sp_configure N'cost threshold for parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Data-warehousing / Reporting server: As queries will be running for long time, it is advised to set the “Maximum Degree of Parallelism” to 0 (zero). This way most of the queries will utilize the parallel processor, and long running queries get a boost in their performance due to multiple processors. EXEC sys.sp_configure N'cost threshold for parallelism', N'0' GO RECONFIGURE WITH OVERRIDE GO Mixed System (OLTP & OLAP): Here is the challenge. The right balance has to be found. I have taken a very simple approach. I set the “Maximum Degree of Parallelism” to 2, which means the query still uses parallelism but only on 2 CPUs. However, I keep the “Cost Threshold for Parallelism” very high. This way, not all the queries will qualify for parallelism but only the query with higher cost will go for parallelism. I have found this to work best for a system that has OLTP queries and also where the reporting server is set up. Here, I am setting ‘Cost Threshold for Parallelism’ to 25 values (which is just for illustration); you can choose any value, and you can find it out by experimenting with the system only. In the following script, I am setting the ‘Max Degree of Parallelism’ to 2, which indicates that the query that will have a higher cost (here, more than 25) will qualify for parallel query to run on 2 CPUs. This implies that regardless of the number of CPUs, the query will select any two CPUs to execute itself. EXEC sys.sp_configure N'cost threshold for parallelism', N'25' GO EXEC sys.sp_configure N'max degree of parallelism', N'2' GO RECONFIGURE WITH OVERRIDE GO Read all the post in the Wait Types and Queue series. Additionally a must read comment of Jonathan Kehayias. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest you all to read the online book for further clarification. All the discussion of Wait Stats over here is generic and it varies from system to system. It is recommended that you test this on the development server before implementing on the production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • SQL SERVER – Migration Assistant Upgraded to Support SQL Server 2014

    - by Pinal Dave
    We all start somewhere when it is about database. There are different reasons, why we go for one database over another database. Usually the reason is cost and convenience. After a period of time when business is successful and traffic is growing, the same two reasons of cost and convenience start to become secondary goals. I have seen quite a lot of companies starting with free databases and after a while switching to another database as they want stability and service from the product company. Microsoft has an excellent product which lets you migrate your database from the alternate database to SQL Server. It is called SQL Server Migration Assistant (SSMA) and earlier this week, it has been upgraded to support SQL Server 2014. Now you can migrate from your database to to all editions of SQL Server 2005, SQL Server 2008, SQL Server 2008 R2, SQL Server 2012 and SQL Server 2014. SQL Server Migration Assistant (SSMA) is a free supported tool from Microsoft. Here is where you can download SSMA v5.3 for various databases. Microsoft SQL Server Migration Assistant v5.3 for Access Microsoft SQL Server Migration Assistant (SSMA) for Access is a tool to automate migration from Microsoft Access database(s) to SQL Server Microsoft SQL Server Migration Assistant v5.3 for Oracle Microsoft SQL Server Migration Assistant (SSMA) for Oracle is a tool to automate migration from Oracle database to SQL Server. Microsoft SQL Server Migration Assistant v5.3 for Sybase Microsoft SQL Server Migration Assistant (SSMA) for Sybase is a tool to automate migration from Sybase ASE database to SQL Server. Microsoft SQL Server Migration Assistant v5.3 for MySQL Microsoft SQL Server Migration Assistant (SSMA) for MySQL is a tool to automate migration from MySQL database to SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: MySQL, PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • SQL SERVER – Changing Default Installation Path for SQL Server

    - by pinaldave
    Earlier I wrote a blog post about SQL SERVER – Move Database Files MDF and LDF to Another Location and in the blog post we discussed how we can change the location of the MDF and LDF files after database is already created. I had mentioned that we will discuss how to change the default location of the database. This way we do not have to change the location of the database after it is created at different locations. The ideal scenario would be to specify this default location of the database files when SQL Server Installation was performed. If you have already installed SQL Server there is an easy way to solve this problem. This will not impact any database created before the change, it will only affect the default location of the database created after the change. To change the default location of the SQL Server Installation follow the steps mentioned below: Go to Right Click on Servers >> Click on Properties >> Go to the Database Settings screen You can change the default location of the database files. All the future database created after the setting is changed will go to this new location. You can also do the same with T-SQL and here is the T-SQL code to do the same. USE [master] GO EXEC xp_instance_regwrite N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'DefaultData', REG_SZ, N'F:\DATA' GO EXEC xp_instance_regwrite N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'DefaultLog', REG_SZ, N'F:\DATA' GO What are the best practices do you follow with regards to default file location for your database? I am interested to know them. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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  • Does it make sense to develop open source python library for database inspection?

    - by gruszczy
    Some time ago I came up with an idea for a library for database inspection. I started developing it and got some very basic functionality, just to check if that's possible. Recently however, I get second thoughts, whether such project would really be useful. I am actually planning to develop following software suite: library for python, that would provide easy interface to inspect database structure, desktop application in PyQt that would use the interface to provide graphical database inspection, web application in Django that would use the interface to provide database inspection through the browser. Do you think such suite would be useful for other developers/database administrators/analysts? I know, that there is pgadmin for PostgreSQL and some tool for sqlite3 and that there is Java tool called DBInspect. Usually I would be against creating new tool and rather join existing project, but I am not Java programmer (and I would rather stick to python or C, which I like) and none of these projects provide a library for database inspection. Anyway I would like to hear some opinions from fellow developers, whether such project make sense or I should try to spend my free time on developing something else.

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  • SQL University: What and why of database testing

    - by Mladen Prajdic
    This is a post for a great idea called SQL University started by Jorge Segarra also famously known as SqlChicken on Twitter. It’s a collection of blog posts on different database related topics contributed by several smart people all over the world. So this week is mine and we’ll be talking about database testing and refactoring. In 3 posts we’ll cover: SQLU part 1 - What and why of database testing SQLU part 2 - What and why of database refactoring SQLU part 2 – Tools of the trade With that out of the way let us sharpen our pencils and get going. Why test a database The sad state of the industry today is that there is very little emphasis on testing in general. Test driven development is still a small niche of the programming world while refactoring is even smaller. The cause of this is the inability of developers to convince themselves and their managers that writing tests is beneficial. At the moment they are mostly viewed as waste of time. This is because the average person (let’s not fool ourselves, we’re all average) is unable to think about lower future costs in relation to little more current work. It’s orders of magnitude easier to know about the current costs in relation to current amount of work. That’s why programmers convince themselves testing is a waste of time. However we have to ask ourselves what tests are really about? Maybe finding bugs? No, not really. If we introduce bugs, we’re likely to write test around those bugs too. But yes we can find some bugs with tests. The main point of tests is to have reproducible repeatability in our systems. By having a code base largely covered by tests we can know with better certainty what a small code change can break in other parts of the system. By having repeatability we can make code changes with confidence, since we know we’ll see what breaks in other tests. And here comes the inability to estimate future costs. By spending just a few more hours writing those tests we’d know instantly what broke where. Imagine we fix a reported bug. We check-in the code, deploy it and the users are happy. Until we get a call 2 weeks later about a certain monthly process has stopped working. What we don’t know is that this process was developed by a long gone coworker and for some reason it relied on that same bug we’ve happily fixed. There’s no way we could’ve known that. We say OK and go in and fix the monthly process. But what we have no clue about is that there’s this ETL job that relied on data from that monthly process. Now that we’ve fixed the process it’s giving unexpected (yet correct since we fixed it) data to the ETL job. So we have to fix that too. But there’s this part of the app we coded that relies on data from that exact ETL job. And just like that we enter the “Loop of maintenance horror”. With the loop eventually comes blame. Here’s a nice tip for all developers and DBAs out there: If you make a mistake man up and admit to it. All of the above is valid for any kind of software development. Keeping this in mind the database is nothing other than just a part of the application. But a big part! One reason why testing a database is even more important than testing an application is that one database is usually accessed from multiple applications and processes. This makes it the central and vital part of the enterprise software infrastructure. Knowing all this can we really afford not to have tests? What to test in a database Now that we’ve decided we’ll dive into this testing thing we have to ask ourselves what needs to be tested? The short answer is: everything. The long answer is: read on! There are 2 main ways of doing tests: Black box and White box testing. Black box testing means we have no idea how the system internals are built and we only have access to it’s inputs and outputs. With it we test that the internal changes to the system haven’t caused the input/output behavior of the system to change. The most important thing to test here are the edge conditions. It’s where most programs break. Having good edge condition tests we can be more confident that the systems changes won’t break. White box testing has the full knowledge of the system internals. With it we test the internal system changes, different states of the application, etc… White and Black box tests should be complementary to each other as they are very much interconnected. Testing database routines includes testing stored procedures, views, user defined functions and anything you use to access the data with. Database routines are your input/output interface to the database system. They count as black box testing. We test then for 2 things: Data and schema. When testing schema we only care about the columns and the data types they’re returning. After all the schema is the contract to the out side systems. If it changes we usually have to change the applications accessing it. One helpful T-SQL command when doing schema tests is SET FMTONLY ON. It tells the SQL Server to return only empty results sets. This speeds up tests because it doesn’t return any data to the client. After we’ve validated the schema we have to test the returned data. There no other way to do this but to have expected data known before the tests executes and comparing that data to the database routine output. Testing Authentication and Authorization helps us validate who has access to the SQL Server box (Authentication) and who has access to certain database objects (Authorization). For desktop applications and windows authentication this works well. But the biggest problem here are web apps. They usually connect to the database as a single user. Please ensure that that user is not SA or an account with admin privileges. That is just bad. Load testing ensures us that our database can handle peak loads. One often overlooked tool for load testing is Microsoft’s OSTRESS tool. It’s part of RML utilities (x86, x64) for SQL Server and can help determine if our database server can handle loads like 100 simultaneous users each doing 10 requests per second. SQL Profiler can also help us here by looking at why certain queries are slow and what to do to fix them.   One particular problem to think about is how to begin testing existing databases. First thing we have to do is to get to know those databases. We can’t test something when we don’t know how it works. To do this we have to talk to the users of the applications accessing the database, run SQL Profiler to see what queries are being run, use existing documentation to decipher all the object relationships, etc… The way to approach this is to choose one part of the database (say a logical grouping of tables that go together) and filter our traces accordingly. Once we’ve done that we move on to the next grouping and so on until we’ve covered the whole database. Then we move on to the next one. Database Testing is a topic that we can spent many hours discussing but let this be a nice intro to the world of database testing. See you in the next post.

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  • Data Guard - Snapshot Standby Database??

    - by Jian Zhang-Oracle
    ?? -------- ?????,??standby?????mount??????????REDO??,??standby????????????????????,???????read-only???open????,????ACTIVE DATA GUARD,????standby?????????(read-only)??(????????),????standby???????????(read-write)? ?????,?????????????Real Application Testing(RAT)??????????,?????????standby??????snapshot standby?????????,??snapshot standby??????????,???????????(read-write)??????snapshot standby??????????????,?????????,??????????,????????,?????????snapshot standby?????standby???,????????? ?? ---------  1.??standby?????? SQL> Alter system set db_recovery_file_dest_size=500M; System altered. SQL> Alter system set db_recovery_file_dest='/u01/app/oracle/snapshot_standby'; System altered. 2.??standby?????? SQL> alter database recover managed standby database cancel; Database altered. 3.??standby???snapshot standby,??open snapshot standby SQL> alter database convert to snapshot standby; Database altered. SQL> alter database open;    Database altered. ??snapshot standby??????SNAPSHOT STANDBY,open???READ WRITE: SQL> select DATABASE_ROLE,name,OPEN_MODE from v$database; DATABASE_ROLE    NAME      OPEN_MODE ---------------- --------- -------------------- SNAPSHOT STANDBY FSDB      READ WRITE 4.?snapshot standby???????????Real Application Testing(RAT)????????? 5.?????,??snapshot standby???physical standby,?????????? SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Database mounted. SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY; Database altered. SQL> shutdown immediate; ORA-01507: database not mounted ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Database mounted. SQL>ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION; Database altered. 5.?????standby?,???????PHYSICAL STANDBY,open???MOUNTED SQL> select DATABASE_ROLE,name,OPEN_MODE from v$database; DATABASE_ROLE    NAME      OPEN_MODE ---------------- --------- -------------------- PHYSICAL STANDBY FSDB      MOUNTED 6.??????????????? ????: SQL> select ads.dest_id,max(sequence#) "Current Sequence",            max(log_sequence) "Last Archived"        from v$archived_log al, v$archive_dest ad, v$archive_dest_status ads        where ad.dest_id=al.dest_id        and al.dest_id=ads.dest_id        and al.resetlogs_change#=(select max(resetlogs_change#) from v$archived_log )        group by ads.dest_id;    DEST_ID Current Sequence Last Archived ---------- ---------------- -------------      1              361           361      2              361           362 --???? SQL>    select al.thrd "Thread", almax "Last Seq Received", lhmax "Last Seq Applied"       from (select thread# thrd, max(sequence#) almax           from v$archived_log           where resetlogs_change#=(select resetlogs_change# from v$database)           group by thread#) al,          (select thread# thrd, max(sequence#) lhmax           from v$log_history           where resetlogs_change#=(select resetlogs_change# from v$database)           group by thread#) lh      where al.thrd = lh.thrd;     Thread Last Seq Received Last Seq Applied ---------- ----------------- ----------------          1               361              361 ??????????,???blog,???????????,??"??:Data Guard - Snapshot Standby Database??" 

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  • What are some good tips for a developer trying to design a scalable MySQL database?

    - by CFL_Jeff
    As the question states, I am a developer, not a DBA. I have experience with designing good ER schemas and am fairly knowledgeable about normalization and good schema design. I have also worked with data warehouses that use dimensional modeling with fact tables and dim tables. However, all of the database-driven applications I've developed at previous jobs have been internal applications on the company's intranet, never receiving "real-world traffic". Furthermore, at previous jobs, I have always had a DBA or someone who knew much more than me about these things. At this new job I just started, I've been asked to develop a public-facing application with a MySQL backend and the data stored by this application is expected to grow very rapidly. Oh, and we don't have a DBA. Well, I guess I am the DBA. ;) As far as designing a database to be scalable, I don't even know where to start. Does anyone have any good tips or know of any good educational materials for a developer who has been sort of shoved into a DBA/database designer role and has been tasked with designing a scalable database to support an application like this? Have any other developers been through this sort of thing? What did you do to quickly become good at this role? I've found some good slides on the subject here but it's hard to glean details from slides. Wish I could've attended that guy's talk. I also found a good blog entry called 5 Ways to Boost MySQL Scalability which had some good information, though some of it was over my head. tl;dr I just want to make sure the database doesn't have to be completely redesigned when it scales up, and I'm looking for tips to get it right the first time. The answer I'm looking for is a "list of things every developer should know about making a scalable MySQL database so your application doesn't perform like crap when the data gets huge".

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  • What does SQL Server trace flag 253 do?

    - by kamens
    In another question I was trying to research how to control SQL Server's query plan caches: http://stackoverflow.com/questions/2593749/is-there-an-equivalent-of-optionrecompile-or-with-recompile-for-an-entire-c ...and I found trace flag 253 via this article: http://www.sqlservercentral.com/Forums/Topic837613-146-1.aspx The article is correct, if I run DBCC TRACEON(253) and then a number of queries, I can manually check the query plan cache and see that plans have not been inserted. If I run DBCC TRACEOFF(253), query plans are cached as normal. So my question is...what else does this flag do? Does anybody know the official story?

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  • MySQL limit from descending order

    - by faya
    Hello, Is it available to write a query to use same "LIMIT (from), (count)", but get result in backwards? In example if I have 8 rows in the table and I want to get 5 rows in two steps I would: first step query: select * from table limit 0, 5 first step result: first 5 rows; second step query: select * from table limit 5, 5 second step result: last 3 rows; But I want to get it vice versa. I mean from the first step I want last 3 rows and from the second I want 5 first rows. Thank you for your answer

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