Question

我需要打印更新查询的回滚查询。我的原始查询是

UPDATE EMPLOYEE SET NAME = 'SAMAN' WHERE ID=4;

上述查询的相应更新是

UPDATE EMPLOYEE SET NAME=(SELECT NAME FROM EMPLOYEE WHERE ID=4);

如果上面的原始查询出错，我需要打印一个回滚查询。我还需要它来通过查询来打印它。我正在使用oracle 11g数据库。

Answer 1

您可以通过运行如下所示的选择查询

来执行此操作

SELECT 'UPDATE EMPLOYEE SET NAME = '''||name||''' WHERE id = '||id||';' FROM employee;

当然，在更新查询之前运行select查询。

Answer 2

据我所知，这是你正在寻找的某种 log 表。我不知道你的意思是“打印回滚查询”;从来没有听说过这样的事情。

所以，让我展示一下我的想法。检查它，如果在您的情况下有意义，请申请。代码被评论，我希望你能理解它

准备场景：

SQL> -- Log table
SQL> create table emp_log
  2    (id    number   constraint pk_el primary key,
  3     empno number   constraint fk_el_emp references emp (empno) not null,
  4     datum date     not null,
  5     ename varchar2(20)
  6    );

Table created.

SQL> -- A sequence which will be used to populate the ID column in the EMP_LOG table
SQL> create sequence seqa;

Sequence created.

SQL> -- Trigger; if new ENAME is different from the last one, log the change (i.e.
SQL> -- store the old ENAME)
SQL> create or replace trigger trg_bu_emp
  2    before update on emp
  3    for each row
  4  begin
  5    if :new.ename <> :old.ename then
  6       insert into emp_log (id, empno, datum, ename)
  7       values (seqa.nextval, :new.empno, sysdate, :old.ename);
  8    end if;
  9  end;
 10  /

Trigger created.

好的，让我们看看它是如何工作的：

SQL> -- Some employees in department 10
SQL> select empno, ename from emp where deptno = 10;

     EMPNO ENAME
---------- ----------
      7782 CLARK
      7839 KING
      7934 MILLER

SQL> -- Update KING's name to a better one (just kidding)
SQL> update emp set ename = 'LITTLEFOOT' where empno = 7839;

1 row updated.

SQL> -- What's in the log?
SQL> select * From emp_log order by id desc;

        ID      EMPNO DATUM               ENAME
---------- ---------- ------------------- --------------------
         5       7839 30.03.2018 20:22:15 KING

SQL> -- I don't like the new name after all; return the previous one
SQL> update emp e set
  2    e.ename = (select l.ename from emp_log l
  3               where l.empno = e.empno
  4                 and l.id = (select max(l1.id) from emp_log l1
  5                             where l1.empno = l.empno
  6                            )
  7              )
  8  where e.empno = 7839;

1 row updated.

SQL> -- What we've done?
SQL> select empno, ename from emp where deptno = 10;

     EMPNO ENAME
---------- ----------
      7782 CLARK
      7839 KING
      7934 MILLER

SQL> -- What's in the log now?
SQL> select * From emp_log order by id desc;

        ID      EMPNO DATUM               ENAME
---------- ---------- ------------------- --------------------
         6       7839 30.03.2018 20:22:33 LITTLEFOOT
         5       7839 30.03.2018 20:22:15 KING

SQL>

使用查询打印更新查询的回滚查询

2 个答案: