近期多次聊到sql_mode的話題，也是多次遇到相關問題，今天就趁熱打鐵，再給大家帶來一個sql_mode的案例分享。

基于業務敏感性的考慮，下面涉及的表、存儲過程等均非真實數據，但并不影響排查過程。

（1）客戶側開發童鞋創建了一個存儲過程，該存儲過程沒有嚴格遵守group by標準語法

session 1：mysql> delimiter //mysql> create procedure test_for_group_by() -> begin -> select k,pad,count(*) from test.test group by k; -> end //Query OK, 0 rows affected (0.01 sec)mysql> delimiter ;

（2）客戶側開發童鞋調用該存儲過程，報錯ERROR 1140；因為當時存儲過程比較復雜，改造起來比較麻煩，所以客戶側選擇修改sql_mode

session 1：mysql> call test_for_group_by();ERROR 1140 (42000): In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ’test.test.k’; this is incompatible with sql_mode=only_full_group_by

（3）客戶側修改完sql_mode，再次執行，發現仍然報錯ERROR 1140

session 2：mysql> set global sql_mode=’STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION’;Query OK, 0 rows affected (0.00 sec)session 1：mysql> call test_for_group_by();ERROR 1140 (42000): In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ’test.test.k’; this is incompatible with sql_mode=only_full_group_by

（4）此時想到，修改系統變量，只對新建連接有效，對已有連接不起作用；于是，讓客戶側重新建立連接，確認系統變量已生效，再次調用存儲過程，但仍然報錯ERROR 1140，重復嘗試幾次都是這個結果

session 3：mysql> show variables like ’sql_mode’;+---------------+------------------------------------------------------------------------------------------------------------------------+| Variable_name | Value |+---------------+------------------------------------------------------------------------------------------------------------------------+| sql_mode | STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |+---------------+------------------------------------------------------------------------------------------------------------------------+1 row in set (0.01 sec)mysql> call test_for_group_by();ERROR 1140 (42000): In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ’test.test.k’; this is incompatible with sql_mode=only_full_group_by

（5）進一步排查，讓客戶側在該會話，執行非標準的group by語句，發現可以正常執行

session 3：mysql> select user,host,count(*) From mysql.user group by user;+---------------+-----------+----------+| user | host | count(*) |+---------------+-----------+----------+| mysql.session | localhost |1 || mysql.sys | localhost |1 || root | localhost |1 || rpl_user | % |1 || test | % |1 |+---------------+-----------+----------+5 rows in set (0.00 sec)

（6）繼續排查發現，該存儲過程的sql_mode，還是包括ONLY_FULL_GROUP_BY，因此執行報錯

session 2：mysql> select routine_catalog,routine_schema,routine_name,routine_type,created,last_altered,sql_mode from routines where routine_name=’test_for_group_by’;+-----------------+----------------+-------------------+--------------+---------------------+---------------------+-------------------------------------------------------------------------------------------------------------------------------------------+| routine_catalog | routine_schema | routine_name | routine_type | created | last_altered| sql_mode |+-----------------+----------------+-------------------+--------------+---------------------+---------------------+-------------------------------------------------------------------------------------------------------------------------------------------+| def | test | test_for_group_by | PROCEDURE | 2020-12-24 12:12:10 | 2020-12-24 12:12:10 | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |+-----------------+----------------+-------------------+--------------+---------------------+---------------------+-------------------------------------------------------------------------------------------------------------------------------------------+1 row in set (0.00 sec)

（7）這里我們也可以知道，系統變量修改只對新建對象有效，對已有對象不生效；解決辦法很簡單，重建該存儲過程即可

session 3：mysql> drop procedure test_for_group_by;Query OK, 0 rows affected (0.01 sec)mysql> delimiter //mysql> create procedure test_for_group_by() -> begin -> select k,pad,count(*) from test.test group by k; -> end //Query OK, 0 rows affected (0.01 sec)mysql> delimiter ;mysql> call test_for_group_by();+--------+-------------------------------------------------------------+----------+| k | pad | count(*) |+--------+-------------------------------------------------------------+----------+| 393975 | 35227182905-15234265621-59793845249-15413569710-23749555118 |1 || 495688 | 09512147864-77936258834-40901700703-13541171421-15205431759 |1 || 497896 | 13152283289-69561545685-52868757241-04245213425-69280254356 |1 || 498573 | 43131080328-59298106536-35954612339-97546855884-75769514803 |1 || 500775 | 27590239742-20204899609-34345212327-79811525340-24267764271 |1 || 501885 | 63188288836-92351140030-06390587585-66802097351-49282961843 |1 || 503330 | 01495266405-82925129145-92643983850-90243995398-18709399387 |1 || 503666 | 40929980986-33813039690-13155419391-97985458477-39771362212 |1 || 504353 | 00505722282-72931248925-57037623248-81117963809-88658076981 |1 || 514246 | 21979564480-87492594656-60524686334-78820761788-57684966682 |1 |+--------+-------------------------------------------------------------+----------+10 rows in set (0.00 sec)Query OK, 0 rows affected (0.00 sec)總結

通過這個案例，我們可以知道，修改sql_mode系統變量，只對新建連接和新建對象(主要包括函數和存儲過程)有效，對已有連接和已有對象不生效。

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