case … when <op> … (extended)

The simple form of case uses an implied equals to (=) comparison. With the extended form, the comparison operator can be specified explicitly.

SELECT CASE <Expression> WHEN < 0 THEN 'negative'
                         WHEN = 0 THEN 'zero'
                                  ELSE 'positive'
        END
  FROM …

Related

• Tutorial: Case — Conditional Expressions

• Better supported alternative: case when … (searched case).

Normative References

The extended case expression is defined in ISO/IEC 9075-2:2023 as optional feature F262, “Extended CASE expression”.