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COALESCE (SQL-92 compatible)
Syntax
COALESCE ( expression1, expression2 [ , ... ] )
Description
The COALESCE scalar function is a type of conditional expression. (See Conditional Expressions for more information and a summary of all the conditional expressions.)
COALESCE specifies a series of expressions, and returns the first expression whose value is not null. If all the expressions evaluate as null, COALESCE returns a null value.
The COALESCE syntax is shorthand notation for a common case that can also be represented in a CASE expression. The following two formulations are equivalent:
COALESCE ( expression1 , expression2 , expression3 )
CASE
WHEN expression1 IS NOT NULL THEN expression1
WHEN expression2 IS NOT NULL THEN expression2
ELSE expression3
Example
SELECT COALESCE(end_date, start_date) from job_hist;
Notes
