【练习】使用事务控制语句

1.使用show engines 命令确定系统中是否有任何事务存储引擎可用以及哪个是默认引擎。

2.使用set autocommit 语句启用autocommit。

3.为使用world数据库做准备，确认city表使用事务存储引擎innodb。

4.使用start transaction 语句显式启动新事务。

5.删除一行。

6.使用rollback语句回滚打开的事务。

1.

mysql> show enginesG
*************************** 1. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: MRG_MYISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 6. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 9. row ***************************
      Engine: FEDERATED
     Support: NO
     Comment: Federated MySQL storage engine
Transactions: NULL
          XA: NULL
  Savepoints: NULL
9 rows in set (0.00 sec)

2.

mysql> set autocommit = 1;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
|            1 |
+--------------+
1 row in set (0.00 sec)

3.

mysql> use world
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

mysql> show create table cityG
*************************** 1. row ***************************
       Table: city
Create Table: CREATE TABLE `city` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `Name` char(35) NOT NULL DEFAULT '',
  `CountryCode` char(3) NOT NULL DEFAULT '',
  `District` char(20) NOT NULL DEFAULT '',
  `Population` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`ID`),
  KEY `CountryCode` (`CountryCode`),
  CONSTRAINT `city_ibfk_1` FOREIGN KEY (`CountryCode`) REFERENCES `country` (`Code`)
) ENGINE=InnoDB AUTO_INCREMENT=4080 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

4.

mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

5.

mysql> select * from city where name = 'manta';
+-----+-------+-------------+----------+------------+
| ID  | Name  | CountryCode | District | Population |
+-----+-------+-------------+----------+------------+
| 600 | Manta | ECU         | Manab铆   |     164739 |
+-----+-------+-------------+----------+------------+
1 row in set (0.01 sec)

mysql> delete from city where name = 'manta';
Query OK, 1 row affected (0.02 sec)

mysql> select * from city where name = 'manta';
Empty set (0.00 sec)

mysql> rollback;
Query OK, 0 rows affected (0.02 sec)

mysql> select * from city where name = 'manta';
+-----+-------+-------------+----------+------------+
| ID  | Name  | CountryCode | District | Population |
+-----+-------+-------------+----------+------------+
| 600 | Manta | ECU         | Manab铆   |     164739 |
+-----+-------+-------------+----------+------------+
1 row in set (0.01 sec)