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sqlfirebirdarithmetic-expressions

Convert string into arithmetic operators

I have an equation stored in a table and want my SQL to return the calculated value.

e.g

Select replace (c.equation, 'x', 121) 
  from config c where key= 2

The above returns (8.5-(121-20)/100) . I need the calculated value ,i.e 7.49

I tried the following but not working :

Select cast(replace (g.equation, 'x', 121) as double precision) 
  from config c where key= 2

Any idea please?

Solution

  • As stated by @Arioch you have to use EXECUTE STATEMENT. Than just put equation in following procedure CALCULATE

    CREATE OR ALTER PROCEDURE calculate (equation VARCHAR(100))
RETURNS (result VARCHAR(10))
AS
begin
  EXECUTE STATEMENT ('SELECT ' || :EQUATION || ' FROM rdb$database')
  INTO :result;

  suspend;
end