分类无法删除

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (`icake`.`category`, CONSTRAINT `pid_fk_category` FOREIGN KEY (`pid`) REFERENCES `category` (`id`))

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)

at com.mysql.jdbc.Util.getInstance(Util.java:408)

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:935)

at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973)

at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909)

at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527)

at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680)

at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2501)

at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1858)

at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1197)

at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:46)

at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:74)

at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:50)

at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)

at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)

at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)

... 36 more