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  • Which index is used in select and why?

    - by Lukasz Lysik
    I have the table with zip codes with following columns: id - PRIMARY KEY code - NONCLUSTERED INDEX city When I execute query SELECT TOP 10 * FROM ZIPCodes I get the results sorted by id column. But when I change the query to: SELECT TOP 10 id FROM ZIPCodes I get the results sorted by code column. Again, when I change the query to: SELECT TOP 10 code FROM ZIPCodes I get the results sorted by code column again. And finally when I change to: SELECT TOP 10 id,code FROM ZIPCodes I get the results sorted by id column. My question is in the title of the question. I know which indexes are used in the queries, but my question is, why those indexes are used? I the second query (SELECT TOP 10 id FROM ZIPCodes) wouldn't it be faster if the clusteder index was used? How the query engine chooses which index to use?

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  • Mysql query to fetch data

    - by hnihar
    i have a table "request" with 4 columns namely: 1.recId :long primary key 2.interactionId:long 3.requestedBy:boolean 4.requestedType:boolean and data is as follows: VALUES (185,455699,0,5), (186,455746,0,1), (187,455746,1,1), (188,455752,0,1), (189,455753,0,1), (190,455753,1,1), (191,455754,1,1) i want a query to fetch all the rows where interactionId is same and having requestedBy both 1 and 0 values and requestType=1; regards, Nihar

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  • Select rows where column LIKE dictionary word

    - by Gerve
    I have 2 tables: Dictionary - Contains roughly 36,000 words CREATE TABLE IF NOT EXISTS `dictionary` ( `word` varchar(255) NOT NULL, PRIMARY KEY (`word`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; Datas - Contains roughly 100,000 rows CREATE TABLE IF NOT EXISTS `datas` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `hash` varchar(32) NOT NULL, `data` varchar(255) NOT NULL, `length` int(11) NOT NULL, `time` int(11) NOT NULL, PRIMARY KEY (`ID`), UNIQUE KEY `hash` (`hash`), KEY `data` (`data`), KEY `length` (`length`), KEY `time` (`time`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=105316 ; I would like to somehow select all the rows from datas where the column data contains 1 or more words. I understand this is a big ask, it would need to match all of these rows together in every combination possible, so it needs the best optimization. I have tried the below query, but it just hangs for ages: SELECT `datas`.*, `dictionary`.`word` FROM `datas`, `dictionary` WHERE `datas`.`data` LIKE CONCAT('%', `dictionary`.`word`, '%') AND LENGTH(`dictionary`.`word`) > 3 ORDER BY `length` ASC LIMIT 15 I have also tried something similar to the above with a left join, and on clause that specified the like statement.

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  • Using SQL Server Views with NHibernate

    - by colinramsay
    I have a site that sells cars. On the frontend, I want to only show cars that are published, and on the backend I want to show all cars. Whether a car is published or not depends on a number of factors, so I wanted to create a view to simplify this. My question is, can I reduce duplication by dynamically telling NHibernate to sometimes use the "PublishedCar" view and something use the "AllCar" view when querying/fetching Car entities?

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  • ASP.MVC ModelBinding Behaviour

    - by OldBoy
    This one has me stumped, despite the numerous posts on here. The scenario is a basic MVC(2) web application with simple CRUD operations. Whenever the edit form is submitted and the UpdateModel() called, an exception is thrown: System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException was unhandled by user code This occurs against a DropDownList value which is a foreign key on the entity table. However, there is another DropDownList list on the form, representing another foreign key, which does not throw the error (unsurprisingly). Changing the property values manually inside the Edit Action: Recipe recipe = repository.GetRecipe(int.Parse(formValues["recipeid"])); recipe.CategoryId = Convert.ToInt32(formValues["CategoryId"].ToString()); recipe.Page = int.Parse(formValues["Page"].ToString()); recipe.PublicationId=Convert.ToInt32(formValues["PublicationId"].ToString()); Allows the CategoryId and Page properties to be updated, and then the error is thrown on the PublicationId. All of the referential integrity is checked an the same in the db and the dbml. Any light shed on this would be most welcome.

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  • How to save to two tables using one SQLAlchemy model

    - by Oatman
    I have an SQLAlchemy ORM class, linked to MySQL, which works great at saving the data I need down to the underlying table. However, I would like to also save the identical data to a second archive table. Here's some psudocode to try and explain what I mean my_data = Data() #An ORM Class my_data.name = "foo" #This saves just to the 'data' table session.add(my_data) #This will save it to the identical 'backup_data' table my_data_archive = my_data my_data_archive.__tablename__ = 'backup_data' session.add(my_data_archive) #And commits them both session.commit() Just a heads up, I am not interested in mapping a class to a JOIN, as in: http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables

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  • Selecting rows distinctively

    - by noway
    Lets assume my database table structure is something like | items | weight | |============|==========| | item_1 | 50 | | item_2 | 90 | | item_2 | 45 | | item_2 | 60 | | item_3 | 40 | In the select statement, I want to show an item only for once with the highest weight also ordered by height. So the result should be : | items | weight | |============|==========| | item_2 | 90 | | item_1 | 50 | | item_3 | 40 | I tried something like SELECT DISTINCT items, weight FROM mytable ORDER BY weight DESC but it didn't work because the results are actually distinct. How can I make that selection?

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  • custom sorting or ordering a table without resorting the whole shebang

    - by fuugus
    for ten years we've been using the same custom sorting on our tables, i'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and would'nt like to have our replication replicate unnecessary entries. i had a look into nested sets, but it does'nt seem to do the job for us. base table: id | a_sort ---+------- 1 10 2 20 3 30 after inserting insert into table (a_sort) values(15) an entry at the second position. id | a_sort ---+------- 1 10 2 20 3 30 4 15 ordering the table with select * from table order by a_sort and resorting all the a_sort entries, updating at least id=(2,3,4) will of course produce the desired output id | a_sort ---+------- 1 10 4 20 2 30 3 40 the column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem. also we've found some pretty neat ways to do this task fast. only; how the heck can we reduce the updates in the db to 1 or 2 max. seems like an awfully common problem. the captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".. but this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)

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  • query to return three records for each customer application based on the options declared in the pre

    - by kumarreddy
    tables look like this table1---customer application columns--- application id--primary key, name, ssn, ... ... table2----balance(actually its a view) columns--- amount balance, application id ...... ...... table3 ---- options columns--- optionid, option value(1,2,3,4), ...... ........ .... table4 ----- ratios columns--- ratios id, option value, ratio value, applicationid(have to think about it), ........ table 4(detail) option value, Ratios 1 ----- 30 1 ----- 40 1 ----- 30 2 ---- 100 2 ----- 0 2 ------ 0 3 ---- 60 3 ------ 30 3 ----- 10 4 ---- 50 4 ----- 30 4 ----- 20 as is the case...now i need to get three records for each customer application with varying balances in proportion of ratios declared in table 4 corresponding to option values...... plz let me know where i was unclear about returning records thanks in advance

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  • Question on different ways to link tables

    - by dotnetdev
    What is the difference between linking two tables and then the PK is an FK in the other table, but the FK has not got the primary key option (so it does not have the gold key), and having the PK in one table as a PK in another table? Am I right to think that the second option is for a many-to-many relationship? Thanks

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  • select row from table and substitute a field with one from another column if not null

    - by EarthMind
    I'm trying construct a PostgreSQL query that does the following but so far my efforts have been in vain. Problem: There are two tables: A and B. I'd like to select all columns from table A (having columns: id, name, description) and substitute the "A.name" column with the value of the column "B.title" from table B (having columns: id, table_A_id title, langcode) where B.table_A_id is 5 and B.langcode is "nl" (if there are any rows). I've tried using a CASE and COALESCE() but failed due to my inexperience with both concepts. Thanks in advance.

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  • Query with multiple IN-statements but without the cartesian product

    - by Janne
    How could I make this kind of query e.g. in MySQL SELECT * FROM Table t WHERE t.a IN (1,2,3) AND t.b IN (4,5,6) AND t.c IN (7,8,9) ... so that the result would contain only the three rows: t.a|t.b|t.c ---+---+--- 1 | 4 | 7 2 | 5 | 8 3 | 6 | 9 The above query of course returns all the combinations of the values in the IN clauses but I would like to get just the ones where the first elements of each tuple match, second elements of each tuple match and so on. Is there any efficient way to do this? By the way is there some common term for this kind of query or concept? I'm having hard time coming up with the question's title because I can't put this into words..

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  • Optimize SQL query (Facebook-like application)

    - by fabriciols
    My application is similar to Facebook, and I'm trying to optimize the query that get user records. The user records are that he as src ou dst. The src is in usermuralentry directly, the dst list are in usermuralentry_user. So, a entry can have one src and many dst. I have those tables: mysql> desc usermuralentry ; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_src_id | int(11) | NO | MUL | NULL | | | private | tinyint(1) | NO | | NULL | | | content | longtext | NO | | NULL | | | date | datetime | NO | | NULL | | | last_update | datetime | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ 10 rows in set (0.10 sec) mysql> desc usermuralentry_user ; +-------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | usermuralentry_id | int(11) | NO | MUL | NULL | | | userinfo_id | int(11) | NO | MUL | NULL | | +-------------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) And the following query to retrieve information from two users. mysql> explain SELECT * FROM usermuralentry AS a , usermuralentry_user AS b WHERE a.user_src_id IN ( 1, 2 ) OR ( a.id = b.usermuralentry_id AND b.userinfo_id IN ( 1, 2 ) ); +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | 1 | SIMPLE | b | ALL | usermuralentry_id,usermuralentry_user_bcd7114e,usermuralentry_user_6b192ca7 | NULL | NULL | NULL | 147188 | | | 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 1371289 | Range checked for each record (index map: 0x1) | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ 2 rows in set (0.00 sec) but it is taking A LOT of time... Some tips to optimize? Can the table schema be better in my application?

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  • Database design -- does it respect 3rd NF?

    - by Flavius
    Hi I have the following relations (tables) in a relational model Person person_id, first_name, last_name, address Student person_id, matr_nr Teacher person_id, salary Lecture lecture_id, lect_name, lect_description Attendees lecture_id, person_id, date I'm wondering about the functional dependencies of Student and Teacher. Do these tables respect the 3rd normal form? Which should be the primary keys of these tables?

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  • Executing sc.exe from .NET Process unable to start and stop service.

    - by Jason
    I'm trying to restart the service from a remote machine. Here is my code. The problem is that I need to enter startinfo.filename = "sc.exe" since I'm putting "start /wait sc" this is causing an error. Here is my code, any thoughts. Also if anyone has any idea how to keep the cmd window open after this is ran so I could see the code that was ran that would be awesome. string strCommandStop1; string strCommandStop2; string strCommandStart1; string strCommandStart2; string strServer = "\\" + txtServerName.Text; string strDb1 = "SqlAgent$" + txtInsName.Text; string strDb2 = "MSSQL$" + txtInsName.Text; strCommandStop1 = @"start /wait sc " + strServer + " Stop " + strDb1; strCommandStop2 = @"start /wait sc " + strServer + " Stop " + strDb2; strCommandStart1 = @"start /wait sc " + strServer + " Start " + strDb2; strCommandStart2 = @"start /wait sc " + strServer + " Start " + strDb1; try { ProcessStartInfo startInfo = new ProcessStartInfo(); startInfo.CreateNoWindow = true; startInfo.Arguments = strCommandStop1; startInfo.Arguments = strCommandStop2; startInfo.Arguments = strCommandStart1; startInfo.Arguments = strCommandStart2; startInfo .FileName = "sc.exe"; Process.Start(startInfo); } catch (Exception e) { MessageBox.Show(e.Message); }

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  • Is SQLlite strong enough to use as wordpress database ?

    - by justjoe
    i'm just curious. so i ask this particular question about SQLite. I haven't use this type of database extensively. but care to explain what is the basic different between SQLite and Mysql ? The reason behind all of this is i just want to know whether it possible to use it to store wordpress data and act as a database ?

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  • pgSQL query error

    - by running4surival
    i tried using this query: "SELECT * FROM guests WHERE event_id=".$id." GROUP BY member_id;" and I'm getting this error: ERROR: column "guests.id" must appear in the GROUP BY clause or be used in an aggregate function can anyone explain how i can work around this?

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  • What is the current status on Microsoft ProClarity?

    - by Ali_Abadani
    I don't really know how to compose this question. My complay has been using Microsoft ProClarity for few years and we have a quite a few users using it publising books and doing ad-hoc analysis. With the new Microsoft BI solutions, it seems like they are completely going away from ProClarity and replacing the OLAP analysis with Excel. I understand the with SharePoint and integration with PerformancePoint and reporting services the dashboards and reports would be done in SharePoint but what about the analysis? Any ideas?

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