mysql 获取所有的月份

SELECT DISTINCT MONTH(order_date) AS month
FROM orders
ORDER BY month;

SELECT DATE_FORMAT(DATE_ADD(0, INTERVAL n MONTH), '%Y-%m') AS month
FROM (
    SELECT @n := @n + 1 AS n
    FROM (SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS a,
         (SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS b,
         (SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS c
    ORDER BY n LIMIT 100
) AS numbers
WHERE DATE_ADD(0, INTERVAL n MONTH) <= CURDATE();

SELECT DISTINCT DATE_FORMAT(order_date, '%Y-%m') AS month
FROM orders
ORDER BY month;

CREATE INDEX idx_order_date ON orders(order_date);