Mysql事務隔離級別_MySQL

來源：懂視網責編：小采時間：2020-11-09 19:51:52

Mysql事務隔離級別_MySQL

Mysql事務隔離級別_MySQL:scott@PROD>select * from dept1; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 50 OPERATIONS BOSTON 20 DBA Bei Jing scott@PROD>update dept1 set deptno=21 where dname='DBA'

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導讀Mysql事務隔離級別_MySQL:scott@PROD>select * from dept1; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 50 OPERATIONS BOSTON 20 DBA Bei Jing scott@PROD>update dept1 set deptno=21 where dname='DBA'

Mysql默認的隔離級別是：

(mysql@localhost) [fandb]> select @@tx_isolation;
+-----------------+
| @@tx_isolation |
+-----------------+
| REPEATABLE-READ |
+-----------------+





session A:
(mysql@localhost) [fandb]> begin;
Query OK, 0 rows affected (0.00 sec)

(mysql@localhost) [fandb]> update per1 set name='fan1' where id=1
 -> ;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

(mysql@localhost) [fandb]> select * from per1 limit 1;
+----+------+
| id | name |
+----+------+
| 1 | fan1 |
+----+------+
1 row in set (0.00 sec)
A會話更新一行




session B:
(mysql@localhost) [fandb]> begin;
Query OK, 0 rows affected (0.00 sec)

(mysql@localhost) [fandb]> select * from per1 limit 1;
+----+------+
| id | name |
+----+------+
| 1 | fan |
+----+------+
1 row in set (0.00 sec)
此時在B開始事務并查詢，id=1的name列并沒有變化




session A:
(mysql@localhost) [fandb]> commit;
Query OK, 0 rows affected (0.00 sec)
接著A會話提交




session B:
(mysql@localhost) [fandb]> select * from per1 limit 1;
+----+------+
| id | name |
+----+------+
| 1 | fan |
+----+------+
1 row in set (0.00 sec)
在去B會話查詢，還是沒有變化




(mysql@localhost) [fandb]> commit;
Query OK, 0 rows affected (0.00 sec)

(mysql@localhost) [fandb]> select * from per1 limit 1;
+----+------+
| id | name |
+----+------+
| 1 | fan1 |
+----+------+
1 row in set (0.00 sec)
只有當B會話事務結束，再次查詢記錄才會變化
 




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        Mysql事務隔離級別_MySQL
        Mysql事務隔離級別_MySQL:scott@PROD>select * from dept1; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 50 OPERATIONS BOSTON 20 DBA Bei Jing scott@PROD>update dept1 set deptno=21 where dname='DBA'
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