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COALESCE¶
Gibt den ersten Nicht-NULL-Ausdruck in den Argumenten zurück oder NULL, wenn alle Argumente NULL sind.
Syntax¶
COALESCE( <expr1> , <expr2> [ , ... , <exprN> ] )
Nutzungshinweise¶
Alle Argumente müssen denselben Datentyp haben.
Sortierungsdetails¶
The collation specifications of all input arguments must be compatible.
The comparisons follow the collation based on the input arguments‘ collations and precedences.
The collation of the result of the function is the highest-precedence collation of the inputs.
Beispiele¶
SELECT column1, column2, column3, coalesce(column1, column2, column3)
FROM (values
(1, 2, 3 ),
(null, 2, 3 ),
(null, null, 3 ),
(null, null, null),
(1, null, 3 ),
(1, null, null),
(1, 2, null)
) v;
+---------+---------+---------+-------------------------------------+
| COLUMN1 | COLUMN2 | COLUMN3 | COALESCE(COLUMN1, COLUMN2, COLUMN3) |
|---------+---------+---------+-------------------------------------|
| 1 | 2 | 3 | 1 |
| NULL | 2 | 3 | 2 |
| NULL | NULL | 3 | 3 |
| NULL | NULL | NULL | NULL |
| 1 | NULL | 3 | 1 |
| 1 | NULL | NULL | 1 |
| 1 | 2 | NULL | 1 |
+---------+---------+---------+-------------------------------------+