Release 10.1A: OpenEdge Data Management:
SQL Reference

> ## 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.

> #### Syntax

>     COALESCE ( expression1, expression2 [... ] )

> 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
>     END

> Example

> This example illustrates the `COALESCE` function:

>     SELECT COALESCE (end_date, start_date) from job_hist;

> #### Notes

> - This function is not allowed in a `GROUP BY` clause.

> - Arguments to this function cannot be query expressions.

> ##### Compatibility

> SQL compatible

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