SQL CASE Statement

he syntax for the case statement is:

CASE  [ expression ]
  WHEN condition_1 THEN result_1
  WHEN condition_2 THEN result_2
  …
  WHEN condition_n THEN result_n
  ELSE result
END

expression is optional. It is the value that you are comparing to the list of conditions. (ie: condition_1, condition_2, … condition_n)

 

select table_name,
CASE owner
  WHEN ‘SYS’ THEN ‘The owner is SYS’
  WHEN ‘SYSTEM’ THEN ‘The owner is SYSTEM’
  ELSE ‘The owner is another value’
END
from all_tables;

or you could rewrite it as

select table_name,
CASE
  WHEN owner=’SYS’ THEN ‘The owner is SYS’
  WHEN owner=’SYSTEM’ THEN ‘The owner is SYSTEM’
  ELSE ‘The owner is another value’
END
from all_tables;

 

Evaluating Two Different Fields:

select supplier_id,
CASE
  WHEN supplier_name = ‘IBM’ and supplier_type = ‘Hardware’ THEN ‘North office’
  WHEN supplier_name = ‘IBM’ and supplier_type = ‘Software’ THEN ‘South office’
END
from suppliers;

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