Difference between revisions of "COALESCE"
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<p>COALESCE takes any number of arguments and returns the first value that is not null. </p> | <p>COALESCE takes any number of arguments and returns the first value that is not null. </p> | ||
<p></p> | <p></p> | ||
| − | <pre style='width: | + | <pre style='width:85ex'> |
COALESCE(x,y,z) = x if x is not NULL | COALESCE(x,y,z) = x if x is not NULL | ||
COALESCE(x,y,z) = y if x is NULL and y is not NULL | COALESCE(x,y,z) = y if x is NULL and y is not NULL | ||
Revision as of 11:13, 16 July 2012
| COALESCE(f1, f2) | ||
|---|---|---|
| Engine | OK | Alternative |
| ingres | Yes | |
| mysql | Yes | IFNULL(f1, f2) |
| oracle | Yes | NVL(f1, f2) |
| postgres | Yes | |
| sqlserver | Yes | |
COALESCE
COALESCE takes any number of arguments and returns the first value that is not null.
COALESCE(x,y,z) = x if x is not NULL COALESCE(x,y,z) = y if x is NULL and y is not NULL COALESCE(a,y,z) = z if x and y are NULL but z is not NULL COALESCE(x,y,z) = NULL if x and y and z are all NULL
COALESCE can be useful when you want to replace a NULL value with some other value. In this example you show the name of the party for each MSP that has a party. For the MSP with no party (such as Canavan, Dennis) you show the string None.
SELECT name, party ,COALESCE(party,'None') AS aff FROM msp WHERE name LIKE 'C%'
See also
