ORACLE之设置事务的属性(TWO)(二)
7698 20-FEB-81 1600 300
30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500
30
7566 JONES MANAGER 7839 02-APR-81 2975
20
EMPNO ENAME JOB MGR HIREDATE SAL COMM
---------- ---------- --------- ---------- --------- ---------- ----------
DEPTNO
----------
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400
30
7698 BLAKE MANAGER 7839 01-MAY-81 2850
30
7782 CLARK MANAGER 7839 09-JUN-81 2450
10
EMPNO ENAME JOB MGR HIREDATE SAL COMM
---------- ---------- --------- ---------- --------- ---------- ----------
DEPTNO
----------
7788 SCOTT ANALYST 7566 19-APR-87 3000
20
7839 KING PRESIDENT 17-NOV-81 5000
10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0
30
EMPNO ENAME JOB MGR HIREDATE SAL COMM
---------- ---------- --------- ---------- --------- ---------- ----------
DEPTNO
----------
7876 ADAMS CLERK 7788 23-MAY-87 1100
20
7900 JAMES CLERK 7698 03-DEC-81 950
30
7902 FORD ANALYST 7566 03-DEC-81 3000
20
EMPNO ENAME JOB MGR HIREDATE SAL COMM
---------- ---------- --------- ---------- --------- ---------- ----------
DEPTNO
----------
7934 MILLER CLERK 7782 23-JAN-82 2100
10
13 rows selected.
SQL>
在另一个事务中修改一个条数据并提交
[sql]
SQL> update emp set sal=1000 where empno=7934;
[sql]
SQL>COMMIT;
那么在查询的时候会出现如下：
[sql]
1* select * from emp
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1000 10
13 rows selected.
SQL>
第二中事务隔离是：set transaction isolation level serializable；
该属性保证了的是在开始本事务dml操作之前的所有数据是已经提交的数据。它控制的是事务中事务的一致性，在开启本隔离后，在本事务中不会出现幻象读，脏读和不可重复读的情况。该属性即应用与报表又更改数据的应用程序中被多次使用。
eg：
[sql]
SQL> set transaction isolation level serialiable;
set transaction isolation level serialiable
*
ERROR at line 1:
ORA-02179: valid options: ISOLATION LEVEL { SERIALIZABLE | READ COMMITTED }
SQL> set transaction isolation level serializable;
Transaction set.
SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- -----