Difference between revisions of "COALESCE"

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<div class='qu'>
<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

Revision as of 14:39, 16 July 2012

Compatibility
COALESCE(f1, f2)
EngineOKAlternative
ingresYes
mysqlYesIFNULL(f1, f2)
oracleYesNVL(f1, f2)
postgresYes
sqlserverYes

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
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