最近在php中操作數據庫時一直出錯，使用
$result = mysqli_query($link, $sql) or die(mysqli_error($link));
該段代碼獲取到異常信息如下：
Expression #1 of ORDER BY clause is not in SELECT list, references column ‘database.table.column’ which is not in SELECT list; this is incompatible with DISTINCT
php中調試輸出的sql語句爲
select distinct orderid,guestname,holder,state from tb_orderinfo where isdeleted=0 order by CreateTime desc
奇怪的是我將該sql語句放到Navicat中執行並不會報錯，執行成功了。
通過查閱資料發現在mysql5.7.5及以上版本實現了對功能依賴的檢測。默認啓用了ONLY_FULL_GROUP_BY SQL模式。在該模式下，
- 我們使用GROUP BY查詢時，出現在SELECT字段後面的只能是GROUP BY後面的分組字段，或使用聚合函數包裹着的字段，否則會報錯如下信息：
Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'database.table.column' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by - 當使用ORDER BY查詢時，不能使用SELECT DISTINCT去重查詢。否則會報錯如下信息：
Expression #1 of ORDER BY clause is not in SELECT list, references column 'database.table.column' which is not in SELECT list; this is incompatible with DISTINCT
解決方法
- 通過命令關閉ONLY_FULL_GROUP_BY SQL模式
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';
set session sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
但該方法在重啓Mysql服務後會失效，重啓服務後會發現ONLY_FULL_GROUP_BY還是存在的。
- 通過修改mysql的配置文件關閉ONLY_FULL_GROUP_BY SQL模式
[mysqld]
sql_mode ='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'