MySQL高階事務

事務隔離級別

檢視mysql系統的事務隔離級別：

mysql> select @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| repeatable-read |
+-----------------------+
1 row in set (0.00 sec)

檢視mysql會話的事務隔離級別：

mysql> select @@tx_isolation;
+-----------------+
| @@tx_isolation |
+-----------------+
| repeatable-read |
+-----------------+
1 row in set (0.00 sec)
mysql> select @@session.tx_isolation;
+------------------------+
| @@session.tx_isolation |
+------------------------+
| repeatable-read |
+------------------------+
1 row in set (0.00 sec)

設定系統的事務隔離級別：

mysql> set global transaction isolation level read committed;
query ok, 0 rows affected (0.00 sec)
mysql> select @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| read-committed |
+-----------------------+
1 row in set (0.00 sec)
mysql> select @@tx_isolation;
+-----------------+
| @@tx_isolation |
+-----------------+
| repeatable-read |
+-----------------+
1 row in set (0.00 sec)

設定會話的事務隔離級別

mysql> set session transaction isolation level read committed;
query ok, 0 rows affected (0.00 sec)
mysql> select @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| read-committed |
+-----------------------+
1 row in set (0.00 sec)
mysql> select @@tx_isolation;
+----------------+
| @@tx_isolation |
+----------------+
| read-committed |
+----------------+
1 row in set (0.00 sec)

mysql預設是自動提交事務的，檢視autocommit變數：

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.01 sec)

設定mysql不自動提交事務：

mysql> set autocommit = 0;
query ok, 0 rows affected (0.00 sec)
mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 0 |
+--------------+
1 row in set (0.01 sec)

使用rollback回滾事務

mysql> select * from t1;
empty set (0.00 sec)
mysql> insert into t1 values (51, 3000);
query ok, 1 row affected (0.00 sec)
mysql> select * from t1;
+----+------+
| a | b |
+----+------+
| 51 | 3000 |
+----+------+
1 row in set (0.00 sec)
mysql> rollback;
query ok, 0 rows affected (0.03 sec)
mysql> select * from t1;
empty set (0.00 sec)
mysql>

使用start transaction;或begin;顯示的開啟乙個事務：

mysql> start transaction;
query ok, 0 rows affected (0.00 sec)
mysql> begin;
query ok, 0 rows affected (0.00 sec)
mysql> insert into t1 values (51, 3000);
query ok, 1 row affected (0.00 sec)
mysql> select * from t1;
+----+------+
| a | b |
+----+------+
| 51 | 3000 |
+----+------+
1 row in set (0.00 sec)
mysql> rollback;
query ok, 0 rows affected (0.04 sec)
mysql> select * from t1;
empty set (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)
mysql> select * from t1;
empty set (0.00 sec)

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