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This article mainly introduces Mysql transaction isolation level content (read submission) handout, hope to give you some knowledge to supplement and update, if there are other problems to understand, you can continue to pay attention to my update article in the industry information. Mysql transaction isolation level read commit

View mysql transaction isolation levels

mysql> show variables like '%isolation%';+---------------+----------------+| Variable_name | Value |+---------------+----------------+| tx_isolation | READ-COMMITTED |+---------------+----------------+1 row in set (0.00 sec)

You can see that the current transaction isolation level is READ-COMMITTED

Let's take a look at the transaction isolation details under the current isolation level and open two query terminals A and B.

Below is an order table with initial data as follows

mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 1 |+---+-------+1 row in set (0.00 sec) Step 1, open transaction mysql> start transaction in both A and B;Query OK, 0 rows affected (0.00 sec) Step 2 Query number value in both terminals

A

mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 1 |+----+--------+1 row in set (0.00 sec)

B

mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 1 |+---+------+1 row in set (0.00 sec) Step 3 Change the number in B to 2, but do not commit the transaction mysql> update `order` set number=2;Query OK, 1 row affected (0.00 sec)Rows matched: 1 Changed: 1 Warnings: 0 Step 4 Query the value in A mysql> select * from `order`;+--+-----+| id | number |+----+--------+| 13 | 1 |+---+------+1 row in set (0.00 sec) Found that the value in A was not modified. Step 5: Submit transaction B and query the value in A again.

B

mysql> commit;Query OK, 0 rows affected (0.01 sec)

A

mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 2 |+---+-------+1 row in set (0.00 sec) Find that the value in A has changed Step 6: Commit the transaction in A and query the values of A and B again.

A

mysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 2 |+----+--------+1 row in set (0.00 sec)

B

mysql> select * from `order`;+----+--------+| id | number |+----+--------+| 13 | 2 |+---+-------+1 row in set (0.00 sec) Found that the values in A and B are changed to 2.

Here's a simple diagram

We can see that when the transaction isolation level is read committed, when the transaction in B commits, even if A does not commit, it can read the result of B's transaction commit. This solves the problem of dirty reading.

The above is the introduction of Mysql transaction isolation level content (read commit) details, more please pay attention to other related articles!

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