Can I use… nullif(…, …)


SQL nullif returns the value of the first argument unless it equals the second argument—then it returns the null value.

SELECT NULLIF(string_value, 'unknown')
  FROM …

The example returns the value of string_value unless it contains the the text unknown—then it returns the SQL null value.0

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Normative References

The nullif expression is defined in ISO/IEC 9075:2016-2 as mandatory feature F261-03.

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Footnotes

0

The rules how strings are match (e.g. case sensitive or not) depend on the effective collation.

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