CAST

Compatibility

CAST(expr AS type)
Engine	OK	Alternative
ingres	Yes
mysql	Yes
oracle	Yes
postgres	Yes
sqlserver	Yes

CAST

CAST allows you to convert from one type to another.

Often a CAST is implicit - for example if you concatenate a string with a number the number will be automatically changed to a string. However sometimes you need to make the CAST explicit.

 CAST(expr TO type) 

In this example we get the population in millions by casting the floating point value to DECIMAL(8,1) - this ensures one decimal place of accuracy. You can also CAST a date to a string to extract components using SUBSTRING or make up another date.

SELECT CAST(population/1000000 
       AS DECIMAL(8,1)) AS a
      ,population/1000000 AS b
  FROM bbc

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