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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743votes
13answers
1.0mviews

SQL update query using joins

I have to update a field with a value which is returned by a join of 3 tables. Example: select im.itemid ,im.sku as iSku ,gm.SKU as GSKU ,mm.ManufacturerId as ManuId ,mm....
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740votes
15answers
732kviews

How do I see what character set a MySQL database / table / column is?

What is the (default) charset for: MySQL database MySQL table MySQL column
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  • 53.2k
738votes
7answers
1.5mviews

'IF' in 'SELECT' statement - choose output value based on column values

SELECT id, amount FROM report I need amount to be amount if report.type='P' and -amount if report.type='N'. How do I add this to the above query?
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  • 13.2k
737votes
39answers
964kviews

How do I get the query builder to output its raw SQL query as a string?

Given the following code: DB::table('users')->get(); I want to get the raw SQL query string that the database query builder above will generate. In this example, it would be SELECT * FROM users. ...
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  • 10.2k
733votes
4answers
283kviews

SQL injection that gets around mysql_real_escape_string()

Is there an SQL injection possibility even when using mysql_real_escape_string() function? Consider this sample situation. SQL is constructed in PHP like this: $login = mysql_real_escape_string(...
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  • 76.7k
730votes
14answers
259kviews

When to use single quotes, double quotes, and backticks in MySQL

I am trying to learn the best way to write queries. I also understand the importance of being consistent. Until now, I have randomly used single quotes, double quotes, and backticks without any real ...
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  • 24k
702votes
8answers
374kviews

postgres: upgrade a user to be a superuser?

In postgres, how do I change an existing user to be a superuser? I don't want to delete the existing user, for various reasons. # alter user myuser ...?
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  • 10.2k
683votes
23answers
799kviews

Solutions for INSERT OR UPDATE on SQL Server

Assume a table structure of MyTable(KEY, datafield1, datafield2...). Often I want to either update an existing record, or insert a new record if it doesn't exist. Essentially: IF (key exists) run ...
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675votes
22answers
798kviews

Get top 1 row of each group

I have a table which I want to get the latest entry for each group. Here's the table: DocumentStatusLogs Table |ID| DocumentID | Status | DateCreated | | 2| 1 | S1 | 7/29/2011 | | 3| ...
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  • 27k
639votes
11answers
1.2mviews

How to insert a line break in a SQL Server VARCHAR/NVARCHAR string

I didn't see any similar questions asked on this topic, and I had to research this for something I'm working on right now. Thought I would post the answer for it in case anyone else had the same ...
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635votes
11answers
394kviews

Skip certain tables with mysqldump

Is there a way to restrict certain tables from the mysqldump command? For example, I'd use the following syntax to dump only table1 and table2: mysqldump -u username -p database table1 table2 > ...
630votes
15answers
1.2mviews

How to select all records from one table that do not exist in another table?

table1 (id, name) table2 (id, name) Query: SELECT name FROM table2 -- that are not in table1 already
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  • 15.8k
628votes
35answers
642kviews

Fetch the row which has the Max value for a column

Table: UserId, Value, Date. I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (...
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  • 6,315
618votes
18answers
924kviews

How do I restore a dump file from mysqldump?

I was given a MySQL database file that I need to restore as a database on my Windows Server 2008 machine. I tried using MySQL Administrator, but I got the following error: The selected file was ...
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610votes
25answers
439kviews

Is it possible to insert multiple rows at a time in an SQLite database?

In MySQL you can insert multiple rows like this: INSERT INTO 'tablename' ('column1', 'column2') VALUES ('data1', 'data2'), ('data1', 'data2'), ('data1', 'data2'), ('data1', 'data2'); ...
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