触发器的实现

（1）建立触发器c_general，如果对C_1表进行操作具备以下功能：

　　当表C_1发生修改时，显示修改前后的记录

　　当向表C_1插入一条记录时，显示插入的记录

　　当表C_1删除一些课程记录时，表SC_1删除和这些课程有关的选修记录

请在相应的部分填写语句以帮助完成触发器c_general-Triggers the realization of (1) the establishment of triggers c_general, if C_1 operating table have the following functions: C_1 occur when the table changes to show the records before and after modifications to the table when C_1 insert a record, the record shows that when the table insert C_1 some courses to delete records, delete, and these form SC_1 elective courses in the corresponding record, please fill out the statement in part to help complete the flip-flop c_general