【MySQL】故障汇总日志 01

Could not connect, server may not be running. Can’t connect to MySQL server on ‘localhost’ (10061)

原因：MySQL服务未启动。
解决：此电脑->右键管理->服务与应用程序->服务->找到MySQL->点击启动。

ERROR 3780 (HY000): Referencing column ‘Department_id’ and referenced column ‘Department_id’ in foreign key constraint ‘teacher_department’ are incompatible.

原因：外键约束引用列与引用列不兼容
解决：导致这个错误的原因有很多，这里优先考虑默认字符集不同。

ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (course.classes, CONSTRAINT fk_cla_depart FOREIGN KEY (Department_id) REFERENCES department (Department_id))

原因：外键约束检查不存在导致的错误。
解决：先去外键约束指向的表中添加相应数据

mysql> delete from department where department_id=‘202’;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (course.classes, CONSTRAINT fk_cla_depart FOREIGN KEY (Department_id) REFERENCES department (Department_id))

原因：子表中存在id=202
解决：先删除department与classes间的外键约束，然后添加约束并将级联选项设置为cascade。
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delete from Person where Id in (select a.Id from Person a, Person b where a.Email=b.Email and  a.Id>b.Id);

MySql报错： You can’t specify target table ‘table name’ for update in FROM clause

错误提示：不能在同一语句中select出表中的某些值，再update这个表。
解决方法:

delete from Person where Id in (select Id from (select a.Id from Person a, Person b where a.Email=b.Email and  a.Id>b.Id) t)

原理是把第一遍的查询结果作为新表t在使用，规避了错误

ERROR 1418 (HY000): This function has none of DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled (you might want to use the less safe log_bin_trust_function_creators variable)

报错原因：mysql的设置默认是不允许创建函数
解决方法：
1，更改全局配置

  SET GLOBAL log_bin_trust_function_creators = 1;  

2、更改配置文件my.cnf

  log-bin-trust-function-creators=1   重启服务生效