在MySQL中，如果需要查詢某個月份的最后一天日期，可以使用以下兩種方法：

-- 方法一：使用LAST_DAY()函數取月底最后一天
SELECT LAST_DAY('2022-05-01');
-- 結果為2022-05-31
-- 方法二：使用DATE_SUB()函數減去一天來取月底最后一天
SELECT DATE_SUB(DATE_ADD('2022-05-01',INTERVAL 1 MONTH), INTERVAL 1 DAY);
-- 結果為2022-05-31

其中，方法一使用MySQL自帶的LAST_DAY()函數來獲取某個日期所在月份的最后一天的日期。

方法二則是通過先使用DATE_ADD()函數來將日期加上一個月，然后再使用DATE_SUB()函數減去一天來獲取該月份的最后一天。

當需要查詢一段時間內，每個月份的最后一天時，可以將以上兩種方法結合使用來實現：

-- 查詢2022年1月至12月份最后一天
SELECT
MONTH(date) AS month, -- 返回月份
LAST_DAY(date) AS last_day
FROM
(SELECT ADDDATE('2022-01-01', INTERVAL (a1 + a10 * 10 + a100 * 100 + a1000 * 1000) MONTH) AS date
FROM
(SELECT 0 AS a1
UNION ALL SELECT 1 AS a1
UNION ALL SELECT 2 AS a1
UNION ALL SELECT 3 AS a1
UNION ALL SELECT 4 AS a1
UNION ALL SELECT 5 AS a1
UNION ALL SELECT 6 AS a1
UNION ALL SELECT 7 AS a1
UNION ALL SELECT 8 AS a1
UNION ALL SELECT 9 AS a1) AS tens,
(SELECT 0 AS a10
UNION ALL SELECT 1 AS a10
UNION ALL SELECT 2 AS a10
UNION ALL SELECT 3 AS a10
UNION ALL SELECT 4 AS a10
UNION ALL SELECT 5 AS a10
UNION ALL SELECT 6 AS a10
UNION ALL SELECT 7 AS a10
UNION ALL SELECT 8 AS a10
UNION ALL SELECT 9 AS a10) AS hundreds,
(SELECT 0 AS a100
UNION ALL SELECT 1 AS a100
UNION ALL SELECT 2 AS a100
UNION ALL SELECT 3 AS a100
UNION ALL SELECT 4 AS a100) AS thousands) AS months;

以上代碼可以查詢出2022年1月至12月份的最后一天，可以根據需求自行修改。