Questions tagged [sql]

Structured Query Language (SQL) is a language for querying databases. Questions should include code examples, table structure, sample data, and a tag for the DBMS implementation (e.g. MySQL, PostgreSQL, Oracle, MS SQL Server, IBM DB2, etc.) being used. If your question relates solely to a specific DBMS (uses specific extensions/features), use that DBMS's tag instead. Answers to questions tagged with SQL should use ISO/IEC standard SQL.

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875votes
11answers
707kviews

How to Join to first row

I'll use a concrete, but hypothetical, example. Each Order normally has only one line item: Orders: OrderGUID OrderNumber ========= ============ {FFB2...} STL-7442-1 {3EC6...} MPT-...
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873votes
28answers
797kviews

How can I list all foreign keys referencing a given table in SQL Server?

I need to remove a highly referenced table in a SQL Server database. How can I get a list of all the foreign key constraints I will need to remove in order to drop the table? (SQL answers preferable ...
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866votes
21answers
1.8mviews

How can I SELECT rows with MAX(Column value), PARTITION by another column in MYSQL?

My table is: id home datetime player resource 1 10 04/03/2009 john 399 2 11 04/03/2009 juliet 244 5 12 04/03/2009 borat 555 3 10 03/03/2009 john 300 4 11 03/03/2009 juliet 200 6 12 03/03/2009 ...
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865votes
21answers
1.3mviews

Reset identity seed after deleting records in SQL Server

I have inserted records into a SQL Server database table. The table had a primary key defined and the auto increment identity seed is set to “Yes”. This is done primarily because in SQL Azure, each ...
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854votes
14answers
1.1mviews

Should I use != or <> for not equal in T-SQL?

I have seen SQL that uses both != and <> for not equal. What is the preferred syntax and why? I like !=, because <> reminds me of Visual Basic.
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836votes
16answers
581kviews

DateTime2 vs DateTime in SQL Server

Which one: datetime datetime2 is the recommended way to store date and time in SQL Server 2008+? I'm aware of differences in precision (and storage space probably), but ignoring those for now, is ...
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  • 10k
835votes
21answers
842kviews

SQL JOIN - WHERE clause vs. ON clause

After reading it, this is not a duplicate of Explicit vs Implicit SQL Joins. The answer may be related (or even the same) but the question is different. What is the difference and what should go in ...
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  • 70.9k
818votes
14answers
464kviews

Count(*) vs Count(1) - SQL Server

Just wondering if any of you people use Count(1) over Count(*) and if there is a noticeable difference in performance or if this is just a legacy habit that has been brought forward from days gone ...
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  • 27.4k
816votes
15answers
3.1mviews

SQL SELECT WHERE field contains words

I need a select which would return results like this: SELECT * FROM MyTable WHERE Column1 CONTAINS 'word1 word2 word3' And I need all results, i.e. this includes strings with 'word2 word3 word1' or '...
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  • 12.1k
797votes
7answers
1.1mviews

SQL multiple column ordering

How can I sort by multiple columns in SQL and in different directions. column1 would be sorted descending, and column2 ascending.
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785votes
15answers
905kviews

How can I do a FULL OUTER JOIN in MySQL?

I want to do a full outer join in MySQL. Is this possible? Is a full outer join supported by MySQL?
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766votes
33answers
504kviews

Fastest Way of Inserting in Entity Framework

I'm looking for the fastest way of inserting into Entity Framework. I'm asking this because of the scenario where you have an active TransactionScope and the insertion is huge (4000+). It can ...
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  • 9,070
751votes
10answers
756kviews

How can I temporarily disable a foreign key constraint in MySQL?

Is it possible to temporarily disable constraints in MySQL? I have two Django models, each with a foreign key to the other one. Deleting instances of a model returns an error because of the foreign ...
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746votes
15answers
770kviews

MySQL Query GROUP BY day / month / year

Is it possible to make a simple query to count how many records I have in a determined period of time like a year, month, or day, having a TIMESTAMP field, like: SELECT COUNT(id) FROM stats WHERE ...
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744votes
11answers
1.3mviews

Rename column SQL Server 2008

I am using SQL Server 2008 and Navicat. I need to rename a column in a table using SQL. ALTER TABLE table_name RENAME COLUMN old_name to new_name; This statement doesn't work.
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