Cannot add or update a child row: a foreign key constraint fails的解决方法

 ERROR 4388 --- [io-10086-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: 
### Error updating database.  Cause: java.sql.SQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`crm`.`cst_customer`, CONSTRAINT `cstsc_KY_base` FOREIGN KEY (`cust_source`) REFERENCES `base_dict` (`dict_type_code`) ON DELETE CASCADE ON UPDATE CASCADE)

解决方法：因为外键关联的字段不是主键，或者是外键关联的字段不具有唯一性，就是是外键关联的字段里有重复的数值，不具备唯一性，导致映射出错。

详细讲解可以参考文章：