- If both expressions have a Period data type or a derived period, the function returns TRUE if the ending bound of the first expression is less than or equal to the beginning bound of the second expression; otherwise, the function returns FALSE.
- If the first expression is a Period expression and the second expression is a DateTime expression, the function returns TRUE if the ending bound of the first expression is less than or equal to the second expression; otherwise, the function returns FALSE.
- If the first expression is a DateTime expression and the second expression has a Period data type, the function returns TRUE if the first expression is less than the beginning bound of the second expression; otherwise, the function returns FALSE.
- If either expression is NULL, the operator returns UNKNOWN.