CASE_N evaluates conditional_expressions from left to right until a condition evaluates to TRUE or UNKNOWN, or until every condition evaluates to FALSE. The position of the first conditional_expression is one and the positions of subsequent conditions increment by one up to n, where n is the total number of conditional expressions.

IF … | THEN … |
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a conditional_expression evaluates to TRUE, and all prior conditions evaluate to FALSE | CASE_N returns the position of the conditional_expression. |

a conditional_expression evaluates to UNKNOWN, and all prior conditions evaluate to FALSE | If NO CASE OR UNKNOWN is specified, CASE_N returns n + 1. If UNKNOWN is specified and NO CASE is not specified, CASE_N returns n + 1. If NO CASE and UNKNOWN are specified, CASE_N returns n + 2. If neither UNKNOWN nor NO CASE OR UNKNOWN is specified, CASE_N returns NULL. |

every conditional_expression evaluates to FALSE | If NO CASE or NO CASE OR UNKNOWN is specified, CASE_N returns n + 1. If neither NO CASE nor NO CASE OR UNKNOWN is specified, CASE_N returns NULL |