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.
673,094
questions
5242
votes
27
answers
2.6m
views
What is the difference between "INNER JOIN" and "OUTER JOIN"?
Also, how do LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN fit in?
- 57.3k
4285
votes
40
answers
5.4m
views
How do I UPDATE from a SELECT in SQL Server?
In SQL Server, it is possible to insert rows into a table with an INSERT.. SELECT statement:
INSERT INTO Table (col1, col2, col3)
SELECT col1, col2, col3
FROM other_table
WHERE sql = 'cool'
Is it ...
- 45.1k
3282
votes
45
answers
3.8m
views
How to add a column with a default value to an existing table in SQL Server?
How can I add a column with a default value to an existing table in SQL Server 2000 / SQL Server 2005?
- 33.9k
2891
votes
7
answers
1.1m
views
How does database indexing work? [closed]
Given that indexing is so important as your data set increases in size, can someone explain how indexing works at a database-agnostic level?
For information on queries to index a field, check out How ...
- 83.8k
2769
votes
27
answers
2.2m
views
How can I prevent SQL injection in PHP?
If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:
$unsafe_variable = $_POST['user_input'];
...
2472
votes
34
answers
3.8m
views
Finding duplicate values in a SQL table
It's easy to find duplicates with one field:
SELECT email, COUNT(email)
FROM users
GROUP BY email
HAVING COUNT(email) > 1
So if we have a table
ID NAME EMAIL
1 John [email protected]
2 Sam ...
- 35.6k
2426
votes
48
answers
3.3m
views
How to concatenate text from multiple rows into a single text string in SQL Server
Consider a database table holding names, with three rows:
Peter
Paul
Mary
Is there an easy way to turn this into a single string of Peter, Paul, Mary?
- 29.3k
2188
votes
47
answers
3.8m
views
How to return only the Date from a SQL Server DateTime datatype
SELECT GETDATE()
Returns: 2008-09-22 15:24:13.790
I want that date part without the time part: 2008-09-22 00:00:00.000
How can I get that?
- 34.5k
2183
votes
2
answers
2.2m
views
What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN? [duplicate]
What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN
in MySQL?
- 33.5k
2035
votes
4
answers
3.5m
views
Inserting multiple rows in a single SQL query? [duplicate]
I have multiple set of data to insert at once, say 4 rows. My table has three columns: Person, Id and Office.
INSERT INTO MyTable VALUES ("John", 123, "Lloyds Office");
INSERT INTO MyTable VALUES ("...
rits
2022
votes
21
answers
1.8m
views
Select first row in each GROUP BY group?
I'd like to select the first row of each set of rows grouped with a GROUP BY.
Specifically, if I've got a purchases table that looks like this:
SELECT * FROM purchases;
My Output:
id
customer
total
...
- 153k
1953
votes
47
answers
1.8m
views
How to query MongoDB with "like"
I want to query something with SQL's like query:
SELECT * FROM users WHERE name LIKE '%m%'
How can I achieve the same in MongoDB? I can't find an operator for like in the documentation.
- 197k
1860
votes
41
answers
580k
views
Table Naming Dilemma: Singular vs. Plural Names [closed]
Academia has it that table names should be the singular of the entity that they store attributes of.
I dislike any T-SQL that requires square brackets around names, but I have renamed a Users table ...
1851
votes
27
answers
3.4m
views
Insert into ... values ( SELECT ... FROM ... )
I am trying to INSERT INTO a table using the input from another table. Although this is entirely feasible for many database engines, I always seem to struggle to remember the correct syntax for the ...
- 42.2k
1846
votes
35
answers
2.6m
views
Insert results of a stored procedure into a temporary table
How do I do a SELECT * INTO [temp table] FROM [stored procedure]? Not FROM [Table] and without defining [temp table]?
Select all data from BusinessLine into tmpBusLine works fine.
select *
into ...
- 21.7k