Questions tagged [subquery]

SQL term used to describe when a SELECT statement is used as part of a larger SQL statement. The larger statement may be DML and is always found within brackets or parenthesis.

Basic example:

SELECT f.column, (SELECT b.col FROM BAR b) AS col2
FROM FOO f

Correlated:

SELECT f.column, (SELECT b.col FROM BAR b WHERE b.col2 = f.col2) AS col2
FROM FOO f

Derived Table/Inline View:

SELECT f.*
FROM (SELECT t.* FROM FOOBAR t) AS f

IN/NOT IN:

SELECT f.*
FROM FOO f
WHERE f.column IN (SELECT b.col FROM BAR b)


SELECT f.*
FROM FOO f
WHERE f.column NOT IN (SELECT b.col FROM BAR b)

EXISTS/NOT EXISTS:

SELECT f.*
FROM FOO f
WHERE EXISTS (SELECT NULL FROM BAR b WHERE b.col = f.column)


SELECT f.*
FROM FOO f
WHERE NOT EXISTS (SELECT NULL FROM BAR b WHERE b.col = f.column)