POSITION returns a value according to the following rules.
| IF … | THEN the result is … |
|---|---|
| either argument is null | null. |
| string_expression_1 has length zero | one. |
| string_expression_1 is a substring within string_expression_2 | the position in string_expression_2 where string_expression_1 starts. |
| none of the preceding is true | zero. |
If the arguments are character types, then regardless of the server character set, the value for POSITION represents the position of a logical character, not a byte position.