SQL Statements and Extensions for the Salesforce Driver : Subqueries : UNIQUE Predicate

UNIQUE Predicate
Purpose
The Unique predicate is used to determine whether duplicate rows exist in a virtual table (one returned from a subquery).
Syntax
UNIQUE (subquery)
Example
SELECT * FROM dept d WHERE UNIQUE
(SELECT deptno FROM emp e WHERE e.deptno = d.deptno)

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