EXISTS condition - Amazon Redshift
SyntaxArgumentsExample
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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

[ 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:

select dateid from date
where exists (
select 1 from sales
where date.dateid = sales.dateid
)
order by dateid;

dateid
--------
1827
1828
1829
...