Ask the Expert

Use CASE to translate a value to a string

Is it possible in SQL to substitute a string if a certain value is returned from a query? For example,

select emp_id from emp_tb

returns

1
2
3

Would it be possible to replace 1 with John and 2 with Mary to give the end result of

John
Mary
3

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Yes, you can stuff a whole raft [syn: batch, deal, flock, good deal, great deal, hatful, heap, lot, mass, mess, mickle, mint, muckle, peck, pile, plenty, pot, quite a little, sight, slew, spate, stack, tidy sum, wad, whole lot, whole slew] of translations into the SELECT if you wish...

select case emp_id 
            when 1 then 'John'
            when 2 then 'Mary'
            else cast(emp_id as char(4))
        end as emp_string 
  from emp_tb

Note that some database systems may require the CAST, but some don't, and will set the datatype of the CASE expression from the first defined expression inside the CASE.


This was first published in August 2004

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