20、MySQL内中文数据乱码的原理及如何防止乱码？（可选）
1. 网站程序字符集 2. 客户端的字符集 3. 服务器端字符集 4. linux客户端字符集 5. 以上都要统一，否则会出现中文乱码如果编译的时候指定了特定的字符集，则以后创建对应字符集的数据库就不需要指定字符集 -DDEFAULT_CHARSET=utf8 \ -DDEFAULT_COLLATION=utf8_general_ci \ -DEXTRA_CHARSETS=gbk,gb2312,utf8,ascii \ 提示：二进制软件包，安装的数据库字符集默认latinl
21.在把id列设置为主键，在Name字段上创建普通索引
mysql> alter table test add primary key(id); mysql> desc test; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int(4) | NO | PRI | 0 | | | age | tinyint(2) | YES | | NULL | | | name | varchar(16) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 3 rows in set (0.00 sec)
添加索引步骤
mysql> alter table test add index index_name(name); create index index_name on test(name);
22.在字段name后插入手机号字段(shouji)，类型char(11)
mysql> alter table test add shouji char(11) after name; Query OK, 3 rows affected (0.05 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> desc test; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | id | int(4) | NO | PRI | 0 | | | age | tinyint(2) | YES | | NULL | | | name | varchar(16) | YES | MUL | NULL | | | shouji | char(11) | YES | | NULL | | +--------+-------------+------+-----+---------+-------+ 4 rows in set (0.00 sec)
23、所有字段上插入2条记录（自行设定数据）
mysql> insert into test values(4,24,'cyh','604419314'),(5,38,'oldboy','123456'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> select * from test; +----+------+-----------+-----------+ | id | age | name | shouji | +----+------+-----------+-----------+ | 1 | NULL | oldgirl | NULL | | 2 | NULL | 老男孩 | NULL | | 3 | NULL | etiantian | NULL | | 4 | 24 | cyh | 604419314 | | 5 | 38 | oldboy | 123456 | +----+------+-----------+-----------+ 5 rows in set (0.00 sec
24、在手机字段上对前8个字符创建普通索引
mysql> alter table test add index index_shouji(shouji(8)); Query OK, 0 rows affected (0.03 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> select * from test; +----+------+-----------+-----------+ | id | age | name | shouji | +----+------+-----------+-----------+ | 1 | NULL | oldgirl | NULL | | 2 | NULL | 老男孩 | NULL | | 3 | NULL | etiantian | NULL | | 4 | 24 | cyh | 604419314 | | 5 | 38 | oldboy | 123456 | +----+------+-----------+-----------+ 5 rows in set (0.00 sec)
25、查看创建的索引及索引类型等信息
mysql> show index from test\G *************************** 1. row *************************** Table: test Non_unique: 0 Key_name: PRIMARY Seq_in_index: 1 Column_name: id Collation: A Cardinality: 5 Sub_part: NULL Packed: NULL Null: Index_type: BTREE Comment: Index_comment: *************************** 2. row *************************** Table: test Non_unique: 1 Key_name: index_name Seq_in_index: 1 Column_name: name Collation: A Cardinality: 5 Sub_part: NULL Packed: NULL Null: YES Index_type: BTREE Comment: Index_comment: *************************** 3. row *************************** Table: test Non_unique: 1 Key_name: index_shouji Seq_in_index: 1 Column_name: shouji Collation: A Cardinality: 5 Sub_part: 8 Packed: NULL Null: YES Index_type: BTREE Comment:Index_comment:3 rows in set (0.00 sec)
26、删除Name，shouji列的索引
alter table test drop index index_name; drop index index_shouji on test; mysql> drop index index_shouji on test; Query OK, 0 rows affected (0.01 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show index from test\G *************************** 1. row *************************** Table: test Non_unique: 0 Key_name: PRIMARY Seq_in_index: 1 Column_name: id Collation: A Cardinality: 5 Sub_part: NULL Packed: NULL Null: Index_type: BTREE Comment: Index_comment: 1 row in set (0.00 sec
27、对Name列的前6个字符以及手机列的前8个字符组建联合索引
mysql> alter table test add index index_name_shouji(name(6),shouji(8)); Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show index from test\G *************************** 1. row *************************** Table: test Non_unique: 0 Key_name: PRIMARY Seq_in_index: 1 Column_name: id Collation: A Cardinality: 5 Sub_part: NULL Packed: NULL Null: Index_type: BTREE Comment: Index_comment: *************************** 2. row *************************** Table: test Non_unique: 1 Key_name: index_name_shouji Seq_in_index: 1 Column_name: name Collation: A Cardinality: 5 Sub_part: 6 Packed: NULL Null: YES Index_type: BTREE Comment:Index_comment: *************************** 3. row ************************** Table: test Non_unique: 1 Key_name: index_name_shouji Seq_in_index: 2 Column_name: shouji Collation: A Cardinality: 5 Sub_part: 8 Packed: NULL Null: YES Index_type: BTREE Comment: Index_comment: 3 rows in set (0.00 sec)
28.查询手机号以135开头的，名字为oldboy的记录（此记录要提前插入）
mysql> select * from test where name='cyh' and shouji like '6044%'; +----+------+------+-----------+ | id | age | name | shouji | +----+------+------+-----------+ | 4 | 24 | cyh | 604419314 | +----+------+------+-----------+ 1 row in set (0.00 sec)
29.查询上述语句的执行计划（是否使用联合索引等）
mysql> explain select * from test where name='cyh' and shouji like '6044%'\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: test type: rangepossible_keys: index_name_shouji key: index_name_shouji key_len: 32 ref: NULL rows: 1 Extra: Using where 1 row in set (0.00 sec)
30、把test表的引擎改成MyISAM
1 row in set (0.00 sec)
本文转自 tianya1993 51CTO博客，原文链接：http://blog.51cto.com/dreamlinux/1835064，如需转载请自行联系原作者
