标签：val sele ODB star 主键 reg 方式 问题 innodb
mysl事务（innodb支持事务处理） 在Mysql控制台使用事务来操作 mysql> begin； ＃开始一个事务 mysql> insert into a (a) values(555); mysql>rollback; 回滚 ， 这样数据是不会写入的 当然如果上面的数据没问题，就输入commit提交命令就行； mysql> use oldboydb 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> begin; （开启事务） Query OK, 0 rows affected (0.00 sec) mysql> select * from student; +----+----------+---------------+------+ | id | name | register_date | sex | +----+----------+---------------+------+ | 1 | ZhanYang | 2018-06-20 | NULL | | 4 | LiuJia | 2018-05-30 | NULL | | 8 | JiaLiu | 2018-06-20 | NULL | | 9 | JiaLiu | 2018-04-20 | NULL | | 10 | gaoyf | 2018-04-20 | NULL | | 11 | zhujh | 2018-04-20 | NULL | | 12 | zhouha | 2018-04-20 | NULL | | 13 | hanzb | 2018-04-21 | M | +----+----------+---------------+------+ 8 rows in set (0.00 sec) mysql> insert into student (name,register_date,sex) values("Alex","2016-05-21","M"); Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into student (name,register_date,sex) values("Jack","2016-05-21","M"); Query OK, 1 row affected (0.00 sec) mysql> select * from student; +----+----------+---------------+------+ | id | name | register_date | sex | +----+----------+---------------+------+ | 1 | ZhanYang | 2018-06-20 | NULL | | 4 | LiuJia | 2018-05-30 | NULL | | 8 | JiaLiu | 2018-06-20 | NULL | | 9 | JiaLiu | 2018-04-20 | NULL | | 10 | gaoyf | 2018-04-20 | NULL | | 11 | zhujh | 2018-04-20 | NULL | | 12 | zhouha | 2018-04-20 | NULL | | 13 | hanzb | 2018-04-21 | M | | 14 | Alex | 2016-05-21 | M | | 15 | Jack | 2016-05-21 | M | +----+----------+---------------+------+ 10 rows in set (0.00 sec) mysql> rollback; （回滚） Query OK, 0 rows affected (0.00 sec) mysql> select * from student; +----+----------+---------------+------+ | id | name | register_date | sex | +----+----------+---------------+------+ | 1 | ZhanYang | 2018-06-20 | NULL | | 4 | LiuJia | 2018-05-30 | NULL | | 8 | JiaLiu | 2018-06-20 | NULL | | 9 | JiaLiu | 2018-04-20 | NULL | | 10 | gaoyf | 2018-04-20 | NULL | | 11 | zhujh | 2018-04-20 | NULL | | 12 | zhouha | 2018-04-20 | NULL | | 13 | hanzb | 2018-04-21 | M | +----+----------+---------------+------+ 8 rows in set (0.00 sec) mysql> begin; Query OK, 0 rows affected (0.00 sec) mysql> insert into student (name,register_date,sex) values("ZhanXing","2018-05-21","M"); Query OK, 1 row affected (0.00 sec) mysql> insert into student (name,register_date,sex) values("XingYan","2018-05-21","M"); Query OK, 1 row affected (0.00 sec) mysql> select * from student; +----+----------+---------------+------+ | id | name | register_date | sex | +----+----------+---------------+------+ | 1 | ZhanYang | 2018-06-20 | NULL | | 4 | LiuJia | 2018-05-30 | NULL | | 8 | JiaLiu | 2018-06-20 | NULL | | 9 | JiaLiu | 2018-04-20 | NULL | | 10 | gaoyf | 2018-04-20 | NULL | | 11 | zhujh | 2018-04-20 | NULL | | 12 | zhouha | 2018-04-20 | NULL | | 13 | hanzb | 2018-04-21 | M | | 16 | ZhanXing | 2018-05-21 | M | | 17 | XingYan | 2018-05-21 | M | +----+----------+---------------+------+ 10 rows in set (0.00 sec) mysql> commit; （从内存写入磁盘） Query OK, 0 rows affected (0.00 sec) mysql> select * from student; +----+----------+---------------+------+ | id | name | register_date | sex | +----+----------+---------------+------+ | 1 | ZhanYang | 2018-06-20 | NULL | | 4 | LiuJia | 2018-05-30 | NULL | | 8 | JiaLiu | 2018-06-20 | NULL | | 9 | JiaLiu | 2018-04-20 | NULL | | 10 | gaoyf | 2018-04-20 | NULL | | 11 | zhujh | 2018-04-20 | NULL | | 12 | zhouha | 2018-04-20 | NULL | | 13 | hanzb | 2018-04-21 | M | | 16 | ZhanXing | 2018-05-21 | M | | 17 | XingYan | 2018-05-21 | M | +----+----------+---------------+------+ 10 rows in set (0.00 sec) MySQL索引： 创建索引 这是最基本的索引，它没有任何限制。它有以下几种创建方式： CREATE INDEX indexName ON mytable(username(length)); 如果是CHAR，VARCHAR类型，length可以小于字段实际长度；如果是BLOB和TEXT类型，必须指定 length。 修改表结构 ALTER mytable ADD INDEX [indexName] ON (username(length)) 创建表的时候直接指定 CREATE TABLE mytable( ID INT NOT NULL, username VARCHAR(16) NOT NULL, INDEX [indexName] (username(length)) ); 删除索引的语法 DROP INDEX [indexName] ON mytable; mysql> mysql> show index from student; （查看索引） +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | student | 0 | PRIMARY | 1 | id | A | 10 | NULL | NULL | | BTREE | | | +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 1 row in set (0.00 sec) mysql> create index index_name on student (name(32)); （创建索引） Query OK, 0 rows affected (0.05 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show index from student; +---------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +---------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | student | 0 | PRIMARY | 1 | id | A | 10 | NULL | NULL | | BTREE | | | | student | 1 | index_name | 1 | name | A | 10 | NULL | NULL | | BTREE | | | +---------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 2 rows in set (0.00 sec) mysql> drop index index_name on student; （删除索引） Query OK, 0 rows affected (0.04 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show index from student; +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | student | 0 | PRIMARY | 1 | id | A | 10 | NULL | NULL | | BTREE | | | +---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 1 row in set (0.00 sec) 唯一索引： 它与前面的普通索引类似，不同的就是：索引列的值必须唯一，但允许有空值。 如果是组合索引，则列值的组合必须唯一。它有以下几种创建方式： 创建索引 CREATE UNIQUE INDEX indexName ON mytable(username(length)) 修改表结构 ALTER mytable ADD UNIQUE [indexName] ON (username(length)) 创建表的时候直接指定 CREATE TABLE mytable( ID INT NOT NULL, username VARCHAR(16) NOT NULL, UNIQUE [indexName] (username(length)) ); 使用ALTER 命令添加和删除索引 有四种方式来添加数据表的索引： ALTER TABLE tbl_name ADD PRIMARY KEY (column_list): 该语句添加一个主键，这意味着索引值必须是唯一的，且不能为NULL。 ALTER TABLE tbl_name ADD UNIQUE index_name (column_list): 这条语句创建索引的值必须是唯一的（除了NULL外，NULL可能会出现多次）。 ALTER TABLE tbl_name ADD INDEX index_name (column_list): 添加普通索引，索引值可出现多次。 ALTER TABLE tbl_name ADD FULLTEXT index_name (column_list):该语句指定了索引为 FULLTEXT ，用于全文索引。 以下实例为在表中添加索引。 mysql> ALTER TABLE testalter_tbl ADD INDEX (c); 你还可以在 ALTER 命令中使用 DROP 子句来删除索引。尝试以下实例删除索引: mysql> ALTER TABLE testalter_tbl DROP INDEX (c);标签：val sele ODB star 主键 reg 方式 问题 innodb
原文地址：http://blog.51cto.com/zhanx/2154926
