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• MySQL Backup - incremental

  - by Tiffany Walker

  I know that you can use mysqldump. I am currently dumping the following way: ${MYSQLDUMP} --single-transaction -u ${MUSER} -h ${MHOST} -p${MPASS} $db | ${GZIP} -9 > $FILE From my understanding this locks the database and prevents any type of use of the database and can even lock up websites. Is there a better way to maybe do daily/hourly backups of the MySQL database should the database be in the 100mbs and even 1gbs in size?

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• Need help recovering a corrupt SQL database

  - by user570079

  I have a very special case that I have been working on for several days. I have a very large SQL Server 2008 database (about 2 TB) that contains 500 filegroups to support very large partitioned tables. Recently we had a catastophic failure on one of the drive and lost several filegroups and the database became in-accessible. We have been doing filegroup backups on a daily basis, but due to other issues, we lost our most recent backup of the log and the primary filegroup. We have all the data backed up but the primary filegroup backup is old. There have been no schema changes since the primary filegroup backup, but the lsn's are now all out of sync and we cannot recover the data. I have tried everything I could think of (and have tried just about every trick and hack I could google) but I still end up at the same point where I get messages saying that the files for filegroup x do not match the primary filegroup. I am now at the point of trying to edit the system tables (we have a separate temporary environment to do this so we are not worried about corrupting any production databases). I have tried updated sys.sysdbreg, sys.sysbrickfiles, and sys.sysprufiles to try to trick SQL into thinking all the files are online, but a "Select * From OPENROWSET(TABLE DBPROP, 5)" shows a different database state from what I see in sys.sysdbreg. I am now thinking I need to somehow edit the headers of the actual data files to try to line up the lsn's with the primary. I appreciate any help anyone can give me here, but please do not respond with things like "you are not supposed to do edit mdf, ndf files...." or "see msdn article....", etc. This is an advanced emergency case and I need a real hack so we can just get to the data in this corrupt database and export to a fresh new database. I know there is a way to do this, but not knowing what the DBPROP system functions does (i.e. does it look at system tables or does it actually open the file) is keeping me from trying to figure out how to fool SQL into allowing me to read these files. Thanks for any help.

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• One to many too much data returned - MySQL

  - by Evan McPeters

  I have 2 related MySQL tables in a one to many relationship. Customers: cust_id, cust_name, cust_notes Orders: order_id, cust_id, order_comments So, if I do a standard join to get all customers and their orders via PHP, I return something like: Jack Black, jack's notes, comments about jack's 1st order Jack Black, jack's notes, comments about jack's 2nd order Simon Smith, simon's notes, comments about simon's 1st order Simon Smith, simon's notes, comments about simon's 2nd order The problem is that *cust_notes* is a text field and can be quite large (a couple of thousand words). So, it seems like returning that field for every order is inneficient. I could use *GROUP_CONCAT* and JOINS to return all *order_comments* on a single row BUT order_comments is a large text field too, so it seems like that could create a problem. Should I just use two separate queries, one for the customers table and one for the orders table? Is there a better way?

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• Django: testing get query

  - by Brant

  Okay, so I am sick of writing this... res = Something.objects.filter(asdf=something) if res: single = res[0] else: single = None if single: # do some stuff I would much rather be able to do something like this: single = Something.objects.filter(asdf=something) if single: #do some stuff I want to be able to grab a single object without testing the filtered results. In other words, when i know there is either going to be 1 or 0 matching entries, I would like to jump right to that entry, otherwise just get a 'None'. The DoesNotExist error that goes along with .get does not always work so well when trying to compress these queries into a single line. Is there any way to do what I have described?

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• What's the fastest way to get CRUD over CGI on a database handle in Perl?

  - by mithaldu

  TL;DR: Want to write CGI::CRUD::Simple (a minimalist interface module for CGI::CRUD), but I want to check first if i overlooked a module that already does that. I usually work with applications that don't have the niceties of having frameworks and such already in place. However, a while ago i found myself in a situation where i was asking myself: "Self, i have a DBI database handle and a CGI query object, isn't there a module somewhere that can use this to give me some CRUD so i can move on and work on other things instead of spending hours writing an interface?" A quick survey on CPAN gave me: CGI::Crud Catalyst::Plugin::CRUD Gantry::Plugins::CRUD Jifty::View::Declare::CRUD CatalystX::CRUD Catalyst::Controller::CRUD CatalystX::CRUD::REST Catalyst::Enzyme Now, I didn't go particularly in-depth when looking at these modules, but, safe the first one, they all seem to require the presence of some sort of framework. Please tell me if i was wrong and i can just plug any of those into a barebones CGI script. CGI::CRUD seemed to do exactly what i wanted, although it did insist on being used through a rather old and C-like script that must be acquired on a different site and then prodded in various ways and manners to produce something useful. I went with that and found that it works pretty neat and that it should be rather easy to write a simple and easy-to-use module that provides a very basic [dbh, cgi IN]-[html OUT] interface to it. However, as my previous survey was rather short and i may have been hasty in dismissing modules or missed others, i find myself wondering whether that would only be duplication of work already done. As such i ponder the question in the title. PS: I tend to be too short in some of my explanations and make too many assumptions that others think about things similarly as me, resulting in leaving out critical details. If you find yourself wondering just what exactly I am thinking about when i say CRUD, please poke me in comments and I'll amend the question.

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• Database design problem: intermediate table between 2 tables may end up with too many results.

  - by SK.

  I have to design a database to handle forms. Basically, a form needs to go through (exactly) 7 people, one by one. Each person can either agree or decline a form. If one declines, the chain stops and the following people don't even get notified that there is a form. Right now I have thought of those 3 tables: FORM, PERSON, and RESPONSE inbetween. However, my first solution sounds too heavy because each form could have up to 7 responses. Here we are with the table inbetween. That means that each successful form has 7 rows in the table RESPONSE. Here we have the responding information directly inside the form. It looks ugly but at least keeps everything as singular as possible. On the bad side I can't track the response dates, but I don't think it is crucial for that matter. What is your opinion on this? I feel like both of them are wrong and I don't know how to fix that. If that matters, I'll be using Oracle 9.

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• Producer/consumer system using database (MySql), is this feasible?

  - by johnrl

  Hi all. I need to use something to coordinate my system with several consumers/producers each running on different machines with different operating systems. I have been researching on using MySql to do this, but it seems ridiculously difficult. My requirements are simple: I want to be able to add or remove consumers/producers at any time and thus they should not depend on each other at all. Naturally a database would separate the two nicely. I have been looking at Q4M message queuing plugin for MySql but it seems complicated to use: I have to recompile it every time I upgrade MySql (can this really be true?) because when I try to install it on Ubuntu 9.10 with MySql 5.1.37 it says "Can't open shared library 'libqueue_engine.so' (errno: 0 API version for STORAGE ENGINE plugin is too different)". There is no precompiled version for MySql 5.1.37 apparently. Also what if I want to run MySql on my windows machine, then I can't rely on this plugin as it only seems to run on Linux and OSX?? I really need some input on how to construct my system best possible.

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• SQL Server - Query Short-Circuiting?

  - by Sam Schutte

  Do T-SQL queries in SQL Server support short-circuiting? For instance, I have a situation where I have two database and I'm comparing data between the two tables to match and copy some info across. In one table, the "ID" field will always have leading zeros (such as "000000001234"), and in the other table, the ID field may or may not have leading zeros (might be "000000001234" or "1234"). So my query to match the two is something like: select * from table1 where table1.ID LIKE '%1234' To speed things up, I'm thinking of adding an OR before the like that just says: table1.ID = table2.ID to handle the case where both ID's have the padded zeros and are equal. Will doing so speed up the query by matching items on the "=" and not evaluating the LIKE for every single row (will it short circuit and skip the LIKE)?

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• Database design for a media server containing movies, music, tv and everything in between?

  - by user364114

  In the near future I am attempting to design a media server as a personal project. MY first consideration to get the project underway is architecture, it will certainly be web based but more specifically than that I am looking for suggestions on the database design. So far I am considering something like the following, where I am using [] to represent a table, the first text is the table name to give an idea of purpose and the items within {} would be fields of the table. Also not, fid is functional id referencing some other table. [Item {id, value/name, description, link, type}] - this could be any entity, single song or whole music album, game, movie - almost see this as a recursive relation, ie. a song is an item but an album that song is part of is also an item or for example a tv season is an item, with multiple items being tv episodes [Type {id, fid, mime type, etc}] - file type specific information - could identify how code handles streaming/sending this item to a user [Location {id, fid, path to file?}] [Users {id, username, email, password, ...? }] - user account information [UAC {id, fid, acess level}] - i almost feel its more flexible to seperate access control permissions form the user accounts themselves [ItemLog {id, fid, fid2, timestamp}] - fid for user id, and fid2 for item id - this way we know what user access what when [UserLog {id, fid, timestamp}] -both are logs for access, whether login or last item access [Quota {id, fid, cap}] - some sort of way to throttle users from queing up the entire site and letting it download ... Suggestions or comments are welcome as the hope is that this project will be a open source project once some code is laid out.

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• Need help with SQL query on SQL Server 2005

  - by Avinash

  We're seeing strange behavior when running two versions of a query on SQL Server 2005: version A: SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = 1234 ORDER BY name ASC version B: DECLARE @Id AS INT; SET @Id = 1234; SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @Id ORDER BY name ASC Both queries return 1000 rows; version A takes on average 15s; version B on average takes 4s. Could anyone help us understand the difference in execution times of these two versions of SQL? If we invoke this query via named parameters using NHibernate, we see the following query via SQL Server profiler: EXEC sp_executesql N'SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @id ORDER BY name ASC', N'@id INT', @id=1234; ...and this tends to perform as badly as version A.

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• Database design and foreign keys: Where should they be added in related tables?

  - by Carvell Fenton

  I have a relatively simple subset of tables in my database for tracking something called sessions. These are academic sessions (think offerings of a particular program). The tables to represent a sessions information are: sessions session_terms session_subjects session_mark_item_info session_marks All of these tables have their own primary keys, and are like a tree, in that sessions have terms, terms have subjects, subjects have mark items, etc. So each on would have at least its "parent's" foreign key. My question is, design wise is it a good idea to include the sessions primary key in the other tables as a foreign key to easily select related session items, or is that too much redundency? If I include the session foreign key (or all parent foreign keys from tables up the heirarchy) in all the tables, I can easily select all the marks for a session. As an example, something like SELECT mark FROM session_marks WHERE sessionID=... If I don't, then I would have to combine selects with something like WHERE something IN (SELECT... Which approach is "more correct" or efficient? Thanks in advance!

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• How to develop for iphone application about "retrieving database file on web"?

  - by coverboy

  Hi...all experts! I'm a newbie to iphone developer. Well, currently, I'm developing iphone for Location Based Service. That application need to have these functions. 1. hierarchical tree-view on navigation bar. 2. list up page 3. detail page for example, Let's say. I have top category like "Restaurant, Hotel, Gift Shop" Second level "New York, LA, London,....." Third Level displays all Data with 1 photo. Fourth Level displays Detail of that "Restaurant or Hotel, Gift shop, ..." So, My Only Interest is "How to retrieve the data from remote database server. not using iphone local one." Because, that locations, and shops should be updated frequently, (you know some shops closed, new shops opens.) So, till now, I figured out that using XML to retrieve data. However, using XML is the most effective way to implement? Is there any other way to accomplish this work? You know, transferring XML data via 3G Network is really slow. XML file have more bytes than plist file. I'm currently a beginner of iphone development. So, please help me find a right way!! And, one more question, if I use xml way. Is it possible to Paging? (First page 10 lists up, below that more button...) well, you might guess each category have hundreds of shops!!

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• [Database] How to model this one-to-one relation?

  - by pbean

  I have several entities which respresent different types of users who need to be able to log in to a particular system. Additionally, they have different types of information associated with them. For example: a "general user", which has an e-mail address and "admin user", which has a workstation number (note that this a hypothetical case). Both entities also share common properties like first name, surname, address and telephone number. Finally, they naturally need to have a (unique) user name and a password to log in. In the application, the user just has to fill in his user name and password, and the functionality of the application changes slightly according to the type of the user. You can imagine that the username needs to be unique for this work. How should I model this effectively? I can't just create two tables, because then I can't force a unique constaint on the user name. I also can't put them all in just one table, because they have different types of specific information associated to them. I think I might need 3 seperate tables, one for "users" (with user name and password), one for the "general users" and another one for the "admin users", but how would the relations between these work? Or is there another solution? (By the way, the target DBMS is MySQL, so I don't think generalization is supported in the database system itself).

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• need help with db-query on sql-server 2005.

  - by Avinash

  We're seeing strange behavior when running two versions of a query on SQL Server 2005: version A: SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = 1234 ORDER BY name ASC version B: DECLARE @Id AS INT; SET @Id = 1234; SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @Id ORDER BY name ASC Both queries return 1000 rows; version A takes on average 15s; version B on average takes 4s. Could anyone help us understand the difference in execution times of these two versions of SQL? If we invoke this query via named parameters using NHibernate, we see the following query via SQL Server profiler: EXEC sp_executesql N'SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @id ORDER BY name ASC', N'@id INT', @id=1234; ...and this tends to perform as badly as version A. Thanks in advance,

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• Question about using an access database as a resource file in Visual Studio.

  - by user354303

  Hi I am trying to embed a Microsoft Access database file into my Class assembly DLL. I want my code to reference the resource file and use it with a ADODB.Connection object. Any body know a simpler way, or an easier way? Or what is wrong with my code, when i added the resource file it added me dataset definitions, but i have no idea what to do with those. The connection string I am trying below is from an automatically generated app.config. I did add the item as a resource... using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using ConsoleApplication1.Resources;//SPPrinterLicenses using System.Data.OleDb; using ADODB; using System.Configuration; namespace ConsoleApplication1 { class SharePointPrinterManager { public static bool IsValidLicense(string HardwareID) { OleDbDataAdapter da = new OleDbDataAdapter(); DataSet ds = new DataSet(); ADODB.Connection adoCn = new Connection(); ADODB.Recordset adoRs = new Recordset(); //**open command below fails** adoCn.Open( @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Resources\SPPrinterLicenses.accdb;Persist Security Info=True", "", "", 1); adoRs.Open("Select * from AllWorkstationLicenses", adoCn, ADODB.CursorTypeEnum.adOpenForwardOnly, ADODB.LockTypeEnum.adLockReadOnly, 1); da.Fill(ds, adoRs, "AllworkstationLicenses"); adoCn.Close(); DataTable dt = new DataTable(); //ds.Tables. return true; } } }

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• Microsoft Access vs Native SQL

  - by ktm5124

  Hypothetical: Let's say you are writing complex queries to a database and it is very important that the data you extracted is the correct result set (e.g., that you didn't mess up a JOIN by not using all the correct keys, and all the other things that can go wrong, et cetera). What would you rather use to do this? Would you write the query using Microsoft Access and its Design View, or would you write it in native SQL using a SQL IDE? What is the better professional choice? Thanks in advance your feedback!

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• How to show useful error messages from a database error callback in Phonegap?

  - by Magnus Smith

  Using Phonegap you can set a function to be called back if the whole database transaction or the individual SQL statement errors. I'd like to know how to get more information about the error. I have one generic error-handling function, and lots of different SELECTs or INSERTs that may trigger it. How can I tell which one was at fault? It is not always obvious from the error message. My code so far is... function get_rows(tx) { tx.executeSql("SELECT * FROM Blah", [], lovely_success, statement_error); } function add_row(tx) { tx.executeSql("INSERT INTO Blah (1, 2, 3)", [], carry_on, statement_error); } function statement_error(tx, error) { alert(error.code + ' / ' + error.message); } From various examples I see the error callback will be passed a transaction object and an error object. I read that .code can have the following values: UNKNOWN_ERR = 0 DATABASE_ERR = 1 VERSION_ERR = 2 TOO_LARGE_ERR = 3 QUOTA_ERR = 4 SYNTAX_ERR = 5 CONSTRAINT_ERR = 6 TIMEOUT_ERR = 7 Are there any other properties/methods of the error object? What are the properties/methods of the transaction object at this point? I can't seem to find a good online reference for this. Certainly not on the Phonegap website!

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• Database PK-FK design for future-effective-date entries?

  - by Scott Balmos

  Ultimately I'm going to convert this into a Hibernate/JPA design. But I wanted to start out from purely a database perspective. We have various tables containing data that is future-effective-dated. Take an employee table with the following pseudo-definition: employee id INT AUTO_INCREMENT ... data fields ... effectiveFrom DATE effectiveTo DATE employee_reviews id INT AUTO_INCREMENT employee_id INT FK employee.id Very simplistic. But let's say Employee A has id = 1, effectiveFrom = 1/1/2011, effectiveTo = 1/1/2099. That employee is going to be changing jobs in the future, which would in theory create a new row, id = 2 with effectiveFrom = 7/1/2011, effectiveTo = 1/1/2099, and id = 1's effectiveTo updated to 6/30/2011. But now, my program would have to go through any table that has a FK relationship to employee every night, and update those FK to reference the newly-effective employee entry. I have seen various postings in both pure SQL and Hibernate forums that I should have a separate employee_versions table, which is where I would have all effective-dated data stored, resulting in the updated pseudo-definition below: employee id INT AUTO_INCREMENT employee_versions id INT AUTO_INCREMENT employee_id INT FK employee.id ... data fields ... effectiveFrom DATE effectiveTo DATE employee_reviews id INT AUTO_INCREMENT employee_id INT FK employee.id Then to get any actual data, one would have to actually select from employee_versions with the proper employee_id and date range. This feels rather unnatural to have this secondary "versions" table for each versioned entity. Anyone have any opinions, suggestions from your own prior work, etc? Like I said, I'm taking this purely from a general SQL design standpoint first before layering in Hibernate on top. Thanks!

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• Is fetching data from database a get-method thing?

  - by theva

  I have a small class that I call Viewer. This class is supposed to view the proper layout of each page or something like that... I have a method called getFirstPage, when called the user of this method will get a setting value for which page is currently set as the first page. I have some code here, I think it works but I am not really shure that I have done it the right way: class Viewer { private $db; private $user; private $firstPage; function __construct($db, $user) { $this->db = $db; if(isset($user)) { $this->user = $user; } else { $this->user = 'default'; } } function getFistPage() { $std = $db->prepare("SELECT firstPage FROM settings WHERE user = ':user'"); $std->execute(array(':user' => $user)); $result = $std->fetch(); $this->firstPage = $result['firstPage']; return $this->firstPage; } } My get method is fetching the setting from databse (so far so good?). The problem is that then I have to use this get method to set the private variable firstPage. It seems like I should have a set method to do this, but I cannot really have a set method that just fetch some setting from database, right? Because the user of this object should be able to assume that there already is a setting defined in the object... How should I do that?

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• Help! The log file for database 'tempdb' is full. Back up the transaction log for the database to fr

  - by michael.lukatchik

  We're running SQL Server 2000. In our database, we have an "Orders" table with approximately 750,000 rows. We can perform simple SELECT statements on this table. However, when we want to run a query like SELECT TOP 100 * FROM Orders ORDER BY Date_Ordered DESC, we receive the following message: Error: 9002, Severity: 17, State: 6 The log file for database 'tempdb' is full. Back up the transaction log for the database to free up some log space. We have other tables in our database which are similar in size of the amount of records that are in the tables (i.e. 700,000 records). On these tables, we can run any queries we'd like and we never receive a message about 'tempdb being full'. To resolve this, we've backed up our database, shrunk the actual database and also shrunk the database and files in the tempdb system database, but this hasn't resolved the issue. The size of our log file is set to autogrow. We're not sure where to go next. Are there any ideas why we still might be receiving this message? Error: 9002, Severity: 17, State: 6 The log file for database 'tempdb' is full. Back up the transaction log for the database to free up some log space.

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• master-slave-slave replication: master will become bottleneck for writes

  - by JMW

  hi, the mysql database has arround 2TB of data. i have a master-slave-slave replication running. the application that uses the database does read (SELECT) queries just on one of the 2 slaves and write (DELETE/INSERT/UPDATE) queries on the master. the application does way more reads, than writes. if we have a problem with the read (SELECT) queries, we can just add another slave database and tell the application, that there is another salve. so it scales well... Currently, the master is running arround 40% disk io due to the writes. So i'm thinking about how to scale the the database in the future. Because one day the master will be overloaded. What could be a solution there? maybe mysql cluster? if so, are there any pitfalls or limitations in switching the database to ndb? thanks a lot in advance... :)

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• BNF – how to read syntax?

  - by Piotr Rodak

  A few days ago I read post of Jen McCown (blog) about her idea of blogging about random articles from Books Online. I think this is a great idea, even if Jen says that it’s not exciting or sexy. I noticed that many of the questions that appear on forums and other media arise from pure fact that people asking questions didn’t bother to read and understand the manual – Books Online. Jen came up with a brilliant, concise acronym that describes very well the category of posts about Books Online – RTFM365. I take liberty of tagging this post with the same acronym. I often come across questions of type – ‘Hey, i am trying to create a table, but I am getting an error’. The error often says that the syntax is invalid. 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT DEFAULT Guid_Default NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); 5 The answer is usually(1), ‘Ok, let me check it out.. Ah yes – you have to put name of the DEFAULT constraint before the type of constraint: 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT Guid_Default DEFAULT NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); Why many people stumble on syntax errors? Is the syntax poorly documented? No, the issue is, that correct syntax of the CREATE TABLE statement is documented very well in Books Online and is.. intimidating. Many people can be taken aback by the rather complex block of code that describes all intricacies of the statement. However, I don’t know better way of defining syntax of the statement or command. The notation that is used to describe syntax in Books Online is a form of Backus-Naur notatiion, called BNF for short sometimes. This is a notation that was invented around 50 years ago, and some say that even earlier, around 400 BC – would you believe? Originally it was used to define syntax of, rather ancient now, ALGOL programming language (in 1950’s, not in ancient India). If you look closer at the definition of the BNF, it turns out that the principles of this syntax are pretty simple. Here are a few bullet points: italic_text is a placeholder for your identifier <italic_text_in_angle_brackets> is a definition which is described further. [everything in square brackets] is optional {everything in curly brackets} is obligatory everything | separated | by | operator is an alternative ::= “assigns” definition to an identifier Yes, it looks like these six simple points give you the key to understand even the most complicated syntax definitions in Books Online. Books Online contain an article about syntax conventions – have you ever read it? Let’s have a look at fragment of the CREATE TABLE statement: 1 CREATE TABLE 2 [ database_name . [ schema_name ] . | schema_name . ] table_name 3 ( { <column_definition> | <computed_column_definition> 4 | <column_set_definition> } 5 [ <table_constraint> ] [ ,...n ] ) 6 [ ON { partition_scheme_name ( partition_column_name ) | filegroup 7 | "default" } ] 8 [ { TEXTIMAGE_ON { filegroup | "default" } ] 9 [ FILESTREAM_ON { partition_scheme_name | filegroup 10 | "default" } ] 11 [ WITH ( <table_option> [ ,...n ] ) ] 12 [ ; ] Let’s look at line 2 of the above snippet: This line uses rules 3 and 5 from the list. So you know that you can create table which has specified one of the following. just name – table will be created in default user schema schema name and table name – table will be created in specified schema database name, schema name and table name – table will be created in specified database, in specified schema database name, .., table name – table will be created in specified database, in default schema of the user. Note that this single line of the notation describes each of the naming schemes in deterministic way. The ‘optionality’ of the schema_name element is nested within database_name.. section. You can use either database_name and optional schema name, or just schema name – this is specified by the pipe character ‘|’. The error that user gets with execution of the first script fragment in this post is as follows: Msg 156, Level 15, State 1, Line 2 Incorrect syntax near the keyword 'DEFAULT'. Ok, let’s have a look how to find out the correct syntax. Line number 3 of the BNF fragment above contains reference to <column_definition>. Since column_definition is in angle brackets, we know that this is a reference to notion described further in the code. And indeed, the very next fragment of BNF contains syntax of the column definition. 1 <column_definition> ::= 2 column_name <data_type> 3 [ FILESTREAM ] 4 [ COLLATE collation_name ] 5 [ NULL | NOT NULL ] 6 [ 7 [ CONSTRAINT constraint_name ] DEFAULT constant_expression ] 8 | [ IDENTITY [ ( seed ,increment ) ] [ NOT FOR REPLICATION ] 9 ] 10 [ ROWGUIDCOL ] [ <column_constraint> [ ...n ] ] 11 [ SPARSE ] Look at line 7 in the above fragment. It says, that the column can have a DEFAULT constraint which, if you want to name it, has to be prepended with [CONSTRAINT constraint_name] sequence. The name of the constraint is optional, but I strongly recommend you to make the effort of coming up with some meaningful name yourself. So the correct syntax of the CREATE TABLE statement from the beginning of the article is like this: 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT Guid_Default DEFAULT NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); That is practically everything you should know about BNF. I encourage you to study the syntax definitions for various statements and commands in Books Online, you can find really interesting things hidden there. Technorati Tags: SQL Server,t-sql,BNF,syntax   (1) No, my answer usually is a question – ‘What error message? What does it say?’. You’d be surprised to know how many people think I can go through time and space and look at their screen at the moment they received the error.

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• I have Oracle SQL Developer Installed, Now What?

  - by thatjeffsmith

  If you’re here because you downloaded a copy of Oracle SQL Developer and now you need help connecting to a database, then you’re in the right place. I’ll show you what you need to get up and going so you can finish your homework, teach yourself Oracle database, or get ready for that job interview. You’ll need about 30 minutes to set everything up…and about 5 years to become proficient with Oracle Oracle Database come with SQL Developer but SQL Developer doesn’t include a database If you install Oracle database, it includes a copy of SQL Developer. If you’re running that copy of SQL Developer, please take a second to upgrade now, as it is WAY out of date. But I’m here to talk to the folks that have downloaded SQL Developer and want to know what to do next. You’ve got it running. You see this ‘Connection’ dialog, and… Where am I connecting to, and who as? You NEED a database Installing SQL Developer does not give you a database. So you’re going to need to install Oracle and create a database, or connect to a database that is already up and running somewhere. Basically you need to know the following: where is this database, what’s it called, and what port is the listener running on? The Default Connection properties in SQL Developer These default settings CAN work, but ONLY if you have installed Oracle Database Express Edition (XE). Localhost is a network alias for 127.0.0.1 which is an IP address that maps to the ‘local’ machine, or the machine you are reading this blog post on. The listener is a service that runs on the server and handles connections for the databases on that machine. You can run a database without a listener and you can run a listener without a database, but you can’t connect to a database on a different server unless both that database and listener are up and running. Each listener ‘listens’ on one or more ports, you need to know the port number for each connection. The default port is 1521, but 1522 is often pretty common. I know all of this sounds very complicated Oracle is a very sophisticated piece of software. It’s not analogous to downloading a mobile phone app and and using it 10 seconds later. It’s not like installing Office/Access either – it requires services, environment setup, kernel tweaks, etc. However. Normally an administrator will setup and install Oracle, create the database, and configure the listener for everyone else to use. They’ll often also setup the connection details for everyone via a ‘TNSNAMES.ORA’ file. This file contains a list of database connection details for folks to browse – kind of like an Oracle database phoneboook. If someone has given you a TNSNAMES.ORA file, or setup your machine to have access to a TNSNAMES file, then you can just switch to the ‘TNS’ connection type, and use the dropdown to select the database you want to connect to. Then you don’t have to worry about the server names, database names, and the port numbers. ORCL – that sounds promising! ORCL is the default SID when creating a new database with the Database Creation Assistant (DBCA). It’s just me, and I need help! No administrator, no database, no nothing. What do you do? You have a few options: Buy a copy of Oracle and download, install, and create a database Download and install XE (FREE!) Download, import, and run our Developer Days Hands-on-Lab (FREE!) If you’re a student (or anyone else) with little to no experience with Oracle, then I recommend the third option. Oracle Technology Network Developer Day: Hands-on Database Application Development Lab The OTN lab runs on a A Virtual Box image which contains: 11gR2 Enterprise Edition copy of Oracle a database and listener running for you to connect to lots of demo data for you to play with SQL Developer installed and ready to connect Some browser based labs you can step through to learn Oracle You download the image, you download and install Virtual Box (also FREE!), then you IMPORT the image you previously downloaded. You then ‘Start’ the image. It will boot a copy of Oracle Enterprise Linux (OEL), start your database, and all that jazz. You can then start up and run SQL Developer inside the image OR you can connect to the database running on the image using the copy of SQL Developer you installed on your host machine. Setup Port Forwarding to Make It Easy to Connect From Your Host When you start the image, it will be assigned an IP address. Depending on what network adapter you select in the image preferences, you may get something that can get out to the internet from your image, something your host machine can see and connect to, or something that kind of just lives out there in a vacuum. You want to avoid the ‘vacuum’ option – unless you’re OK with running SQL Developer inside the Linux image. Open the Virtual Box image properties and go to the Networking options. We’re going to setup port forwarding. This will tell your machine that anything that happens on port 1521 (the default Oracle Listener port), should just go to the image’s port 1521. So I can connect to ‘localhost’ and it will magically get transferred to the image that is running. Oracle Virtual Box Port Forwarding 1521 listener database Now You Just Need a Username and Password The default passwords on this image are all ‘oracle’ – so you can connect as SYS, HR, or whatever – just use ‘oracle’ as the password. The Linux passowrds are all ‘oracle’ too, so you can login as ‘root’ or as ‘oracle’ in the Linux desktop. Connect! Connect as HR to your Oracle database running on the OTN Developer Days Virtual Box image If you’re connecting to someone else’s database, you need to ask the person that manages that environment to create for you an account. Don’t try to ‘guess’ or ‘figure out’ what the username and password is. Introduce yourself, explain your situation, and ask kindly for access. This is your first test – can you connect? I know it’s hard to get started with Oracle. There are however many things we offer to make this easier. You’ll need to do a bit of RTM first though. Once you know what’s required, you will be much more likely to succeed. Of course, if you need help, you know where to find me

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• Storing large data in HTTP Session (Java Application)

  - by Umesh Awasthi

  I am asking this question in continuation with http-session-or-database-approach. I am planning to follow this approach. When user add product to cart, create a Cart Model, add items to cart and save to DB. Convert Cart model to cart data and save it to HTTP session. Any update/ edit update underlying cart in DB and update data snap shot in Session. When user click on view cart page, just pick cart data from Session and display to customer. I have following queries regarding HTTP Session How good is it to store large data (Shopping Cart) in Session? How scalable this approach can be ? (With respect to Session) Won't my application going to eat and demand a lot of memory? Is my approach is fine or do i need to consider other points while designing this? Though, we can control what all cart data should be stored in the Session, but still we need to have certain information in cart data being stored in session?

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• How to detach a sql server 2008 database that is not in database list?

  - by Amir

  I installed SQL Server 2008 on Windows 7. Then I created a database. After 2 days I reinstalled Windows and SQL Server. Now I am trying to attach my database file, but I have encountered the error below. I think that the files are like an attached file and I can't attach them. What is difference between an attached file and a non-attached file? How can I attach this file? Please Help Me. Error Text: TITLE: Microsoft SQL Server Management Studio Attach database failed for Server 'AMIR-PC'. (Microsoft.SqlServer.Smo) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.50.1600.1+((KJ_RTM).100402-1540+)&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Attach+database+Server&LinkId=20476 ------------------------------ ADDITIONAL INFORMATION: An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) Unable to open the physical file "F:\Company.mdf". Operating system error 5: "5(Access is denied.)". (Microsoft SQL Server, Error: 5120) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.50.1600&EvtSrc=MSSQLServer&EvtID=5120&LinkId=20476

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