POSITION returns a value according to the following rules.
| Situation | Result |
|---|---|
| Either argument is NULL. | NULL. |
| string_expression_1 has length zero, | One. |
| string_expression_1 is a substring within string_expression_2. | 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.