Mysql事务隔离级别_MySQL

来源：懂视网责编：小采时间：2020-11-09 19:51:52

Mysql事务隔离级别_MySQL

Mysql事务隔离级别_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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导读Mysql事务隔离级别_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默认的隔离级别是：

(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会话更新一行




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)
此时在B开始事务并查询，id=1的name列并没有变化




session A:
(mysql@localhost) [fandb]> commit;
Query OK, 0 rows affected (0.00 sec)
接着A会话提交




session B:
(mysql@localhost) [fandb]> select * from per1 limit 1;
+----+------+
| id | name |
+----+------+
| 1 | fan |
+----+------+
1 row in set (0.00 sec)
在去B会话查询，还是没有变化




(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)
只有当B会话事务结束，再次查询记录才会变化

    

    
    
        Mysql事务隔离级别_MySQL
        Mysql事务隔离级别_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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                        级别
                        mysql
                        事务
                    
                
            
             
                    
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