Oracle database triggers realize data backup and synchronization

a need

When raising wages for employees, automatically back up the new work to the backup table.
 
two code
  1. --触发器应用场景4:数据库的备份和同步
  2. --当给员工涨工资,自动备份新的工资到备份表中
  3. --创建备份表,
  4. /*
  5. create table emp_back as select * from emp;
  6. */
  7. create or replace trigger sync_salay
  8. after update
  9. on emp
  10. for each row
  11. begin
  12. --当主表更新后,自动更新备份表
  13. update EMP_BACK set sal=:new.sal where empno =:new.empno;
  14. end;
 
Three verification
  1. SQL>select sal from emp where empno=7839;
  2. SAL
  3. ----------
  4. 12101
  5. SQL>select sal from emp_back where empno=7839;
  6. SAL
  7. ----------
  8. 12101
  9. SQL> update emp set sal=sal+10where empno=7839;
  10. 已更新1行。
  11. SQL>select sal from emp where empno=7839;
  12. SAL
  13. ----------
  14. 12111
  15. SQL>select sal from emp_back where empno=7839;
  16. SAL
  17. ----------
  18. 12111

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