MySql date subtraction returns the number of months

MySql date subtraction returns the number of months 1. PERIOD_DIFF (P1, P2) returns the number of months between the period P1 and P2 (the format of P1 and P2 is YYMM or YYYYMM). Example: SELECT PERIOD_DIFF (DATE_FORMAT (g. VALIDITY, '% Y % m'), DATE_FORMAT (NOW (),' % Y % m') AS r FROM table name g 2. obtain the year and month of the date, respectively. The total month is year * 12 + monthSELECT DATEDIFF (g. VALIDITY, CURDATE () AS d, g. VALIDITY, (YEAR (g. VALIDITY)-YEAR (CURDATE () * 12 as y, MONTH (g. VALIDITY)-MONTH (CURDATE () AS m, (YEAR (g. VALIDITY)-YEAR (CURDATE () * 12 + MONTH (g. VALIDITY)-MONTH (CURDATE () AS resultFROM table name gWHERE (YEAR (g. VALIDITY)-YEAR (CURDATE () * 12 + MONTH (g. VALIDITY)-MONTH (CURDATE () <48;