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Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

EXISTS Condition

EXISTS conditions test for the existence of rows in a subquery, and return true if a subquery returns at least one row. If NOT is specified, the condition returns true if a subquery returns no rows.

Syntax

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[ NOT ] EXISTS (table_subquery)

Arguments

EXISTS

Is true when the table_subquery returns at least one row.

NOT EXISTS

Is true when the table_subquery returns no rows.

table_subquery

A subquery that evaluates to a table with one or more columns and one or more rows.

Example

This example returns all date identifiers, one time each, for each date that had a sale of any kind:

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select dateid from date where exists ( select 1 from sales where date.dateid = sales.dateid ) order by dateid; dateid -------- 1827 1828 1829 ...

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