Difference between revisions of "COALESCE"
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<tr><td align='center'>'''Engine'''</td><td align='center'>'''OK'''</td><td align='center'>'''Alternative'''</td></tr> | <tr><td align='center'>'''Engine'''</td><td align='center'>'''OK'''</td><td align='center'>'''Alternative'''</td></tr> | ||
<tr><td align='left'>ingres</td><td>Yes</td><td></td></tr> | <tr><td align='left'>ingres</td><td>Yes</td><td></td></tr> | ||
| − | <tr><td align='left'>mysql</td><td>Yes</td><td>[[IFNULL(f1, f2)]]</td></tr> | + | <tr><td align='left'>mysql</td><td>Yes</td><td>[[IFNULL |IFNULL(f1, f2)]]</td></tr> |
| − | <tr><td align='left'>oracle</td><td>Yes</td><td>[[NVL(f1, f2)]]</td></tr> | + | <tr><td align='left'>oracle</td><td>Yes</td><td>[[NVL |NVL(f1, f2)]]</td></tr> |
<tr><td align='left'>postgres</td><td>Yes</td><td></td></tr> | <tr><td align='left'>postgres</td><td>Yes</td><td></td></tr> | ||
<tr><td align='left'>sqlserver</td><td>Yes</td><td></td></tr> | <tr><td align='left'>sqlserver</td><td>Yes</td><td></td></tr> | ||
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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 | ||
| − | COALESCE( | + | COALESCE(x,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(x,y,z) = NULL if x and y and z are all NULL | ||
</pre> | </pre> | ||
| − | <div class=' | + | <div class='ht'> |
| + | <div class=params>schema:gisq</div> | ||
COALESCE can be useful when you want to replace a NULL value with some other value. | 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. | 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. | For the MSP with no party (such as Canavan, Dennis) you show the string None. | ||
| + | <source lang='sql' class='def e-oracle'> | ||
| + | SELECT name, party | ||
| + | ,COALESCE(party,'None') AS aff | ||
| + | FROM gisq.msp WHERE name LIKE 'C%' | ||
| + | </source> | ||
<source lang='sql' class='def'> | <source lang='sql' class='def'> | ||
SELECT name, party | SELECT name, party | ||
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<ul> | <ul> | ||
<li>[[CASE |CASE function]]</li> | <li>[[CASE |CASE function]]</li> | ||
| − | <li>[[NULLIF function]]</li> | + | <li>[[NULLIF |NULLIF function]]</li> |
| − | <li>[[NVL | + | <li>[[NVL |NVL function]]</li> |
</ul> | </ul> | ||
| + | |||
| + | {{Languages}} | ||
Latest revision as of 10:04, 1 October 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(x,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
schema:gisq
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 gisq.msp WHERE name LIKE 'C%'
SELECT name, party ,COALESCE(party,'None') AS aff FROM msp WHERE name LIKE 'C%'
See also
| Language: | English • Deutsch |
|---|
