Case and searched case

In Teiid Spring Boot, to include conditional logic in a scalar expression, you can use the following two forms of the CASE expression:

  • CASE <expr> ( WHEN <expr> THEN <expr>)+ [ELSE expr] END

  • CASE ( WHEN <criteria> THEN <expr>)+ [ELSE expr] END

Each form allows for an output based on conditional logic. The first form starts with an initial expression and evaluates WHEN expressions until the values match, and outputs the THEN expression. If no WHEN is matched, the ELSE expression is output. If no WHEN is matched and no ELSE is specified, a null literal value is output. The second form (the searched case expression) searches the WHEN clauses, which specify an arbitrary criteria to evaluate. If any criteria evaluates to true, the THEN expression is evaluated and output. If no WHEN is true, the ELSE is evaluated or NULL is output if none exists.

Example case statements
SELECT CASE columnA WHEN '10' THEN 'ten' WHEN '20' THEN 'twenty' END AS myExample

SELECT CASE WHEN columnA = '10' THEN 'ten' WHEN columnA = '20' THEN 'twenty' END AS myExample

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