MySQL表相关操作小结
备注:测试数据库版本为MySQL 8.0
这个blog我们来聊聊MySQL 表相关操作
文章目录
- 一.创建表
- 1.1 Table Name
- 1.2 Temporary Tables
- 1.3 Table Cloning and Copying
- 1.4 Column Data Types and Attributes
- 1.5 Indexes, Foreign Keys, and CHECK Constraints
- 1.6 Table Options
- 1.6.1 ENGINE
- 1.6.2 AVG_ROW_LENGTH MAX_ROWS
- 1.6.3 CHARACTER SET COLLATE
- 1.6.4 COMMENT
- 1.6.5 COMPRESSION
- 1.6.6 STATS_AUTO_RECALC STATS_PERSISTENT STATS_SAMPLE_PAGES
- 1.7 Table Partitioning
- 二.修改表
- 2.1 修改表的存储引擎
- 2.2 修改表自增值
- 2.3 修改表的字符集
- 2.4 修改表的备注信息
- 2.5 重命名、重新定义和重新排序列
- 2.6 约束相关
- 2.7 修改表和列的字符集
- 三.删除表
一.创建表
语法:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
[table_options]
[partition_options]
[IGNORE | REPLACE]
[AS] query_expression
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
{ LIKE old_tbl_name | (LIKE old_tbl_name) }
create_definition: {
col_name column_definition
| {INDEX | KEY} [index_name] [index_type] (key_part,...)
[index_option] ...
| {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...)
[index_option] ...
| [CONSTRAINT [symbol]] PRIMARY KEY
[index_type] (key_part,...)
[index_option] ...
| [CONSTRAINT [symbol]] UNIQUE [INDEX | KEY]
[index_name] [index_type] (key_part,...)
[index_option] ...
| [CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (col_name,...)
reference_definition
| check_constraint_definition
}
column_definition: {
data_type [NOT NULL | NULL] [DEFAULT {literal | (expr)} ]
[AUTO_INCREMENT] [UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
[COLLATE collation_name]
[COLUMN_FORMAT {FIXED | DYNAMIC | DEFAULT}]
[STORAGE {DISK | MEMORY}]
[reference_definition]
[check_constraint_definition]
| data_type
[COLLATE collation_name]
[GENERATED ALWAYS] AS (expr)
[VIRTUAL | STORED] [NOT NULL | NULL]
[UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
[reference_definition]
[check_constraint_definition]
}
data_type:
(see Chapter 11, Data Types)
key_part: {col_name [(length)] | (expr)} [ASC | DESC]
index_type:
USING {BTREE | HASH}
index_option: {
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
| {VISIBLE | INVISIBLE}
}
check_constraint_definition:
[CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED]
reference_definition:
REFERENCES tbl_name (key_part,...)
[MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT
table_options:
table_option [[,] table_option] ...
table_option: {
AUTO_INCREMENT [=] value
| AVG_ROW_LENGTH [=] value
| [DEFAULT] CHARACTER SET [=] charset_name
| CHECKSUM [=] {0 | 1}
| [DEFAULT] COLLATE [=] collation_name
| COMMENT [=] 'string'
| COMPRESSION [=] {'ZLIB' | 'LZ4' | 'NONE'}
| CONNECTION [=] 'connect_string'
| {DATA | INDEX} DIRECTORY [=] 'absolute path to directory'
| DELAY_KEY_WRITE [=] {0 | 1}
| ENCRYPTION [=] {'Y' | 'N'}
| ENGINE [=] engine_name
| INSERT_METHOD [=] { NO | FIRST | LAST }
| KEY_BLOCK_SIZE [=] value
| MAX_ROWS [=] value
| MIN_ROWS [=] value
| PACK_KEYS [=] {0 | 1 | DEFAULT}
| PASSWORD [=] 'string'
| ROW_FORMAT [=] {DEFAULT | DYNAMIC | FIXED | COMPRESSED | REDUNDANT | COMPACT}
| STATS_AUTO_RECALC [=] {DEFAULT | 0 | 1}
| STATS_PERSISTENT [=] {DEFAULT | 0 | 1}
| STATS_SAMPLE_PAGES [=] value
| TABLESPACE tablespace_name [STORAGE {DISK | MEMORY}]
| UNION [=] (tbl_name[,tbl_name]...)
}
partition_options:
PARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY [ALGORITHM={1 | 2}] (column_list)
| RANGE{(expr) | COLUMNS(column_list)}
| LIST{(expr) | COLUMNS(column_list)} }
[PARTITIONS num]
[SUBPARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY [ALGORITHM={1 | 2}] (column_list) }
[SUBPARTITIONS num]
]
[(partition_definition [, partition_definition] ...)]
partition_definition:
PARTITION partition_name
[VALUES
{LESS THAN {(expr | value_list) | MAXVALUE}
|
IN (value_list)}]
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'string' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
[TABLESPACE [=] tablespace_name]
[(subpartition_definition [, subpartition_definition] ...)]
subpartition_definition:
SUBPARTITION logical_name
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'string' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
[TABLESPACE [=] tablespace_name]
query_expression:
SELECT ... (Some valid select or union statement)
MySQL的建表语句的语法太长了，看起来都觉得好麻烦
下面将建表的语法分解开
1.1 Table Name
| 类型 | 描述 |
|---|---|
| Table Name | 创建的表名称 举例: 1.tbl_name 2.db_name.tbl_name 3.’ mydb'.’mytbl' |
| IF NOT EXISTS | 如表名已存在 不报错 |
-- 用三种不同的表名的格式来创建表
create table t1(id int,name varchar(100));
create table test1.t2(id int,name varchar(100));
create table `test1`.`t3`(id int,name varchar(100));
-- 创建同名的表 if not exists未报错 有警告 且表为进行覆盖，依旧是原来的表
create table t1(id int,name varchar(100));
create table if not exists t1(id int,name varchar(100),type varchar(100));
show warnings\G
show create table t1\G
执行记录:
mysql> drop table t1,t2,t3;
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
mysql> -- 用三种不同的表名的格式来创建表
mysql> create table t1(id int,name varchar(100));
Query OK, 0 rows affected (0.02 sec)
mysql> create table test1.t2(id int,name varchar(100));
Query OK, 0 rows affected (0.02 sec)
mysql> create table `test1`.`t3`(id int,name varchar(100));
Query OK, 0 rows affected (0.02 sec)
mysql> -- 创建同名的表 if not exists未报错 有警告 且表为进行覆盖，依旧是原来的表
mysql> create table t1(id int,name varchar(100));
ERROR 1050 (42S01): Table 't1' already exists
mysql> create table if not exists t1(id int,name varchar(100),type varchar(100));
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> show warnings\G
*************************** 1. row ***************************
Level: Note
Code: 1050
Message: Table 't1' already exists
1 row in set (0.00 sec)
mysql> show create table t1\G
*************************** 1. row ***************************
Table: t1
Create Table: CREATE TABLE `t1` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
1.2 Temporary Tables
MySQL的临时表与Oracle的全局临时表存在一定的差异
MySQL的临时表仅限当前的session有效，其它session即看不到表也看不到数据
InnoDB存储引擎不支持压缩的临时表
innodb_file_per-table 对临时表不会生效 临时表默认存储在 #innodb_temp 目录
-- session A:创建临时表
CREATE TEMPORARY TABLE new_tbl SELECT * FROM orig_tbl LIMIT 0;
show create table tmp_1\G
insert into tmp_1 (id,name) values (1,'abc');
select * from tmp_1;
-- session B: 查询临时表 提示表不存在
select * from tmp_1;
执行记录:
-- Session A:
mysql> create temporary table tmp_1(id int,name varchar(100));
Query OK, 0 rows affected (0.01 sec)
mysql> show create table tmp_1\G
*************************** 1. row ***************************
Table: tmp_1
Create Table: CREATE TEMPORARY TABLE `tmp_1` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql> insert into tmp_1 (id,name) values (1,'abc');
Query OK, 1 row affected (0.01 sec)
mysql> select * from tmp_1;
+------+------+
| id | name |
+------+------+
| 1 | abc |
+------+------+
1 row in set (0.00 sec)
-- Session B:
mysql> use test1;
Database changed
mysql>
mysql> select * from tmp_1;
ERROR 1146 (42S02): Table 'test1.tmp_1' doesn't exist
1.3 Table Cloning and Copying
表的克隆和拷贝
-- 建表，不拷贝数据 表结构和约束都会同时拷贝
CREATE TABLE new_tbl LIKE orig_tbl;
-- 建表，同时拷贝数据 表结构和数据会拷贝 表约束不会拷贝
CREATE TABLE new_tbl AS SELECT * FROM orig_tbl;
create table test1 (id int auto_increment primary key,name varchar(100));
insert into test1(name) values ('abc');
select * from test1;
show create table test1;
-- like拷贝表定义
create table t_like like test1;
select * from t_like;
show create table t_like;
-- ctas 拷贝数据，主键约束没有过来
create table t_ctas as select * from test1;
select * from test1;
show create table t_ctas;
执行记录:
mysql> create table test1 (id int auto_increment primary key,name varchar(100));
Query OK, 0 rows affected (0.03 sec)
mysql> insert into test1(name) values ('abc');
Query OK, 1 row affected (0.01 sec)
mysql>
mysql> select * from test1;
+----+------+
| id | name |
+----+------+
| 1 | abc |
+----+------+
1 row in set (0.00 sec)
mysql>
mysql> show create table test1;
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------+
| Table | Create Table
|
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------+
| test1 | CREATE TABLE `test1` (
`id` int NOT NULL AUTO_INCREMENT,
`name` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------+
1 row in set (0.01 sec)
mysql>
mysql>
mysql>
mysql> create table t_like like test1;
Query OK, 0 rows affected (0.03 sec)
mysql> select * from t_like;
Empty set (0.01 sec)
mysql> show create table t_like;
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------
-----+
| Table | Create Table
|
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------
-----+
| t_like | CREATE TABLE `t_like` (
`id` int NOT NULL AUTO_INCREMENT,
`name` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------
-----+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> create table t_ctas as select * from test1;
Query OK, 1 row affected (0.03 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from test1;
+----+------+
| id | name |
+----+------+
| 1 | abc |
+----+------+
1 row in set (0.00 sec)
mysql>
mysql> show create table t_ctas;
+--------+----------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+--------+----------------------------------------------------------------------------------------------------------------------------------+
| t_ctas | CREATE TABLE `t_ctas` (
`id` int NOT NULL DEFAULT '0',
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+----------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
1.4 Column Data Types and Attributes
| 类别 | 描述 |
|---|---|
| data_type | 列数据类型 |
| NOT NULL or NULL | 是否可以为空 |
| DEFAULT | 给列一个默认值 |
| AUTO_INCREMENT | 自动增长 当你insert一个null or 0 到一个自增列，会自动生产序列的下一个值 |
| COMMENT | 注释语句 |
| COLUMN_FORMAT | 列的格式(NDB) |
| STORAGE | 存储(NDB) |
| GENERATED ALWAYS | 基于现有列生产的列 |
-- 测试 not null、default、auto_increment、comment
create table user_info(id int primary key auto_increment comment '主键自增id',idcard varchar(50) not null comment '身份证号码',sex varchar(10) default '未知' comment '性别' );
show create table user_info\G
insert into user_info(id,idcard,sex) values(0,'123456','男');
insert into user_info(id,idcard,sex) values(null,'123456',null);
insert into user_info(id,idcard,sex) values(5,'123456','女');
-- insert的时候 没有指定 或者给null 和 0 的时候 自增列会是序列的下一个值
-- 当指定了之后，就是指定的值，而且序列的下一个值也会因为指定的这个值 而发生变化
select * from user_info;
-- 对于有指定default的列 给''/null 都不会触发默认值，只有录入的时候不指定列 才会触发default条件
insert into user_info(id,idcard,sex) values(null,'123456','');
insert into user_info(id,idcard) values(null,'123456');
select * from user_info;
执行记录:
mysql> create table user_info(id int primary key auto_increment comment '主键自增id',idcard varchar(50) not null comment '身份证号码',sex varchar(10) default '
未知' comment '性别' );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> show create table user_info\G
*************************** 1. row ***************************
Table: user_info
Create Table: CREATE TABLE `user_info` (
`id` int NOT NULL AUTO_INCREMENT COMMENT '主键自增id',
`idcard` varchar(50) NOT NULL COMMENT '身份证号码',
`sex` varchar(10) DEFAULT '未知' COMMENT '性别',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql> insert into user_info(id,idcard,sex) values(0,'123456','男');
Query OK, 1 row affected (0.01 sec)
mysql> insert into user_info(id,idcard,sex) values(null,'123456',null);
Query OK, 1 row affected (0.01 sec)
mysql> insert into user_info(id,idcard,sex) values(5,'123456','女');
Query OK, 1 row affected (0.01 sec)
mysql> select * from user_info;
+----+--------+------+
| id | idcard | sex |
+----+--------+------+
| 1 | 123456 | 男 |
| 2 | 123456 | NULL |
| 5 | 123456 | 女 |
+----+--------+------+
3 rows in set (0.00 sec)
mysql> insert into user_info(id,idcard,sex) values(null,'123456','');
Query OK, 1 row affected (0.01 sec)
mysql> select * from user_info;
+----+--------+------+
| id | idcard | sex |
+----+--------+------+
| 1 | 123456 | 男 |
| 2 | 123456 | NULL |
| 5 | 123456 | 女 |
| 6 | 123456 | |
+----+--------+------+
4 rows in set (0.00 sec)
mysql> insert into user_info(id,idcard) values(null,'123456');
Query OK, 1 row affected (0.01 sec)
mysql> select * from user_info;
+----+--------+---------+
| id | idcard | sex |
+----+--------+---------+
| 1 | 123456 | 男 |
| 2 | 123456 | NULL |
| 5 | 123456 | 女 |
| 6 | 123456 | |
| 7 | 123456 | 未知 |
+----+--------+---------+
5 rows in set (0.00 sec)
GENERATED ALWAYS
CREATE TABLE t4 (
first_name VARCHAR(10),
last_name VARCHAR(10),
full_name VARCHAR(255) AS (CONCAT(first_name,' ',last_name))
);
insert into t4(first_name,last_name) values ('马','云');
select * from t4;
insert into t4(first_name,last_name,'full_name') values ('马','化腾','马化腾');
执行记录:
mysql> CREATE TABLE t4 (
-> first_name VARCHAR(10),
-> last_name VARCHAR(10),
-> full_name VARCHAR(255) AS (CONCAT(first_name,' ',last_name))
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> insert into t4(first_name,last_name) values ('马','云');
Query OK, 1 row affected (0.01 sec)
mysql> select * from t4;
+------------+-----------+-----------+
| first_name | last_name | full_name |
+------------+-----------+-----------+
| 马 | 云 | 马 云 |
+------------+-----------+-----------+
1 row in set (0.00 sec)
mysql> insert into t4(first_name,last_name,'full_name') values ('马','化腾','马化腾');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''full
_name') values ('马','化腾','马化腾')' at line 1
mysql>
1.5 Indexes, Foreign Keys, and CHECK Constraints
| 类别 | 描述 |
|---|---|
| CONSTRAINT | 约束 |
| PRIMARY KEY | 主键约束 |
| KEY or INDEX | 索引 key是index的同义词 |
| UNIQUE | 唯一约束 |
| FULLTEXT | 全文索引 |
| SPATIAL | 空间索引 |
| FOREIGN KEY | 外键 |
| CHECK | 检查约束 |
| key_part | 升序or降序 前缀 |
| index_type | 索引类别 |
| index_option | KEY_BLOCK_SIZE、WITH PARSER、COMMENT |
| reference_definition | 外键约束 指定主表的列 |
索引一般是创建表之后再创建，这个地方先略过，后面会单独写一个索引的blog
1.NOT NULL ：非空，用于保证该字段的值不能为空。
2.DEFAULT：默认值，用于保证该字段有默认值。
3.PRIMARY KEY：主键，用于保证该字段的值具有唯一性并且非空。
4.UNIQUE：唯一，用于保证该字段的值具有唯一性，可以为空。
5.CHECK：检查约束，检查字段的值是否为指定的值。
6.FOREIGN KEY：外键，用于限制两个表的关系，用于保证该字段的值必须来自于主表的关联列的值，在从表添加外键约束，用于引用主表中某些的值。
create table user_info
(id int primary key auto_increment comment '主键自增id',
idcard varchar(50) unique not null comment '身份证号码' ,
sex varchar(10) check(sex = '男' or sex = '女') default '男' comment '性别'
);
show create table user_info\G
--
insert into user_info(id,idcard,sex) values (1,'123','abc');
insert into user_info(id,idcard,sex) values (0,'123','男');
insert into user_info(id,idcard,sex) values (0,'123','');
insert into user_info(id,idcard) values (0,'123');
insert into user_info(id,idcard) values (0,'456');
执行记录:
mysql> create table user_info
-> (id int primary key auto_increment comment '主键自增id',
-> idcard varchar(50) unique not null comment '身份证号码' ,
-> sex varchar(10) check(sex = '男' or sex = '女') default '男' comment '性别'
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> show create table user_info\G
*************************** 1. row ***************************
Table: user_info
Create Table: CREATE TABLE `user_info` (
`id` int NOT NULL AUTO_INCREMENT COMMENT '主键自增id',
`idcard` varchar(50) NOT NULL COMMENT '身份证号码',
`sex` varchar(10) DEFAULT '男' COMMENT '性别',
PRIMARY KEY (`id`),
UNIQUE KEY `idcard` (`idcard`),
CONSTRAINT `user_info_chk_1` CHECK (((`sex` = _utf8mb3'男') or (`sex` = _utf8mb3'女')))
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql>
mysql>
-- 违反 检查约束
mysql> insert into user_info(id,idcard,sex) values (1,'123','abc');
ERROR 3819 (HY000): Check constraint 'user_info_chk_1' is violated.
-- 正常录入数据
mysql> insert into user_info(id,idcard,sex) values (0,'123','男');
Query OK, 1 row affected (0.01 sec)
--''一样也违反检查约束，并不会触发default值
mysql> insert into user_info(id,idcard,sex) values (0,'123','');
ERROR 3819 (HY000): Check constraint 'user_info_chk_1' is violated.
-- 违反idcard的唯一约束
mysql> insert into user_info(id,idcard) values (0,'123');
ERROR 1062 (23000): Duplicate entry '123' for key 'user_info.idcard'
mysql>
mysql>
-- 正常录入数据
mysql> insert into user_info(id,idcard) values (0,'456');
Query OK, 1 row affected (0.01 sec)
1.6 Table Options
| 类别 | 描述 |
|---|---|
| ENGINE | 指定存储引擎 |
| AUTO_INCREMENT | 自动增长 |
| AVG_ROW_LENGTH | 平均行长度 |
| [DEFAULT] CHARACTER SET | 指定字符集 |
| CHECKSUM | MyISAM引擎独有的 快速查找损坏的表 |
| [DEFAULT] COLLATE | 指定的排序规则 |
| COMMENT | 表的备注 |
| COMPRESSION | 表压缩 |
| CONNECTION | FEDERATED 存储引擎表 远程连接 |
| DATA DIRECTORY, INDEX DIRECTORY | 数据及索引目录 |
| DELAY_KEY_WRITE | 延迟更新索引到表关闭 |
| ENCRYPTION | 加密 |
| INSERT_METHOD | Merge存储引擎独有 |
| KEY_BLOCK_SIZE | index key blocks(MyISAM), 压缩表的page size(InnoDB) |
| MAX_ROWS | 计划表录入最多的数据行数 |
| MIN_ROWS | 计划表录入最少的数据行数 |
| PACK_KEYS | MyISAM独有 |
| PASSWORD | 未使用 |
| ROW_FORMAT | 指定数据行的物理存储 |
| STATS_AUTO_RECALC | 统计信息相关 |
| STATS_PERSISTENT | 统计信息相关 |
| STATS_SAMPLE_PAGES | 统计信息相关 |
| TABLESPACE | 表空间 |
| UNION | 仅在Merge存储引擎的时候生效 |
1.6.1 ENGINE
常见存储引擎 InnoDB、MyISAM、MEMORY、CSV、ARCHIVE、EXAMPLE、FEDERATED、HEAP、MERGE、NDB
MySQL 8.0之后，连系统表也有MyISAM改为InnoDB，InnoDB已经可以覆盖大部分应用场景了
其它的存储引擎也有各自的使用场景，后面单独写一个blog来简单介绍存储引擎。
1.6.2 AVG_ROW_LENGTH MAX_ROWS
用来控制行的长度和行的总数。
1.6.3 CHARACTER SET COLLATE
字符集和排序规则，MySQL 字符集和排序规则
1.6.4 COMMENT
表的备注，根据规范，表都需要有备注信息
1.6.5 COMPRESSION
表的压缩，节约空间，但是会消耗select 和DML语句的性能
适用于不会被访问的历史归档数据
1.6.6 STATS_AUTO_RECALC STATS_PERSISTENT STATS_SAMPLE_PAGES
STATS_PERSISTENT
指定是否为InnoDB表启用持久统计信息。
DEFAULT：表示表的持久统计信息设置由innodb_stats_persistent配置选项确定
1：表示启用表的持久统计信息
0：关闭此功能
STATS_AUTO_RECALC
指定是否自动重新计算InnoDB表的持久统计信息。
DEFAULT：表示表的持久统计信息设置由innodb_stats_auto_recalc配置选项确定
1：表示表中10％的数据发生更改时将重新计算统计信息
0：禁用自动重新计算此表
STATS_SAMPLE_PAGES
指定在估计索引列的基数和其他统计信息时要采样的索引页数
1.7 Table Partitioning
分区又是另外一个范畴了，会单独开一个blog，此处略过
二.修改表
语法:
ALTER TABLE tbl_name
[alter_option [, alter_option] ...]
[partition_options]
alter_option: {
table_options
| ADD [COLUMN] col_name column_definition
[FIRST | AFTER col_name]
| ADD [COLUMN] (col_name column_definition,...)
| ADD {INDEX | KEY} [index_name]
[index_type] (key_part,...) [index_option] ...
| ADD {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name]
(key_part,...) [index_option] ...
| ADD [CONSTRAINT [symbol]] PRIMARY KEY
[index_type] (key_part,...)
[index_option] ...
| ADD [CONSTRAINT [symbol]] UNIQUE [INDEX | KEY]
[index_name] [index_type] (key_part,...)
[index_option] ...
| ADD [CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (col_name,...)
reference_definition
| ADD [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED]
| DROP {CHECK | CONSTRAINT} symbol
| ALTER {CHECK | CONSTRAINT} symbol [NOT] ENFORCED
| ALGORITHM [=] {DEFAULT | INSTANT | INPLACE | COPY}
| ALTER [COLUMN] col_name
{SET DEFAULT {literal | (expr)} | DROP DEFAULT}
| ALTER INDEX index_name {VISIBLE | INVISIBLE}
| CHANGE [COLUMN] old_col_name new_col_name column_definition
[FIRST | AFTER col_name]
| [DEFAULT] CHARACTER SET [=] charset_name [COLLATE [=] collation_name]
| CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
| {DISABLE | ENABLE} KEYS
| {DISCARD | IMPORT} TABLESPACE
| DROP [COLUMN] col_name
| DROP {INDEX | KEY} index_name
| DROP PRIMARY KEY
| DROP FOREIGN KEY fk_symbol
| FORCE
| LOCK [=] {DEFAULT | NONE | SHARED | EXCLUSIVE}
| MODIFY [COLUMN] col_name column_definition
[FIRST | AFTER col_name]
| ORDER BY col_name [, col_name] ...
| RENAME COLUMN old_col_name TO new_col_name
| RENAME {INDEX | KEY} old_index_name TO new_index_name
| RENAME [TO | AS] new_tbl_name
| {WITHOUT | WITH} VALIDATION
}
partition_options:
partition_option [partition_option] ...
partition_option: {
ADD PARTITION (partition_definition)
| DROP PARTITION partition_names
| DISCARD PARTITION {partition_names | ALL} TABLESPACE
| IMPORT PARTITION {partition_names | ALL} TABLESPACE
| TRUNCATE PARTITION {partition_names | ALL}
| COALESCE PARTITION number
| REORGANIZE PARTITION partition_names INTO (partition_definitions)
| EXCHANGE PARTITION partition_name WITH TABLE tbl_name [{WITH | WITHOUT} VALIDATION]
| ANALYZE PARTITION {partition_names | ALL}
| CHECK PARTITION {partition_names | ALL}
| OPTIMIZE PARTITION {partition_names | ALL}
| REBUILD PARTITION {partition_names | ALL}
| REPAIR PARTITION {partition_names | ALL}
| REMOVE PARTITIONING
}
key_part: {col_name [(length)] | (expr)} [ASC | DESC]
index_type:
USING {BTREE | HASH}
index_option: {
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
| {VISIBLE | INVISIBLE}
}
table_options:
table_option [[,] table_option] ...
table_option: {
AUTO_INCREMENT [=] value
| AVG_ROW_LENGTH [=] value
| [DEFAULT] CHARACTER SET [=] charset_name
| CHECKSUM [=] {0 | 1}
| [DEFAULT] COLLATE [=] collation_name
| COMMENT [=] 'string'
| COMPRESSION [=] {'ZLIB' | 'LZ4' | 'NONE'}
| CONNECTION [=] 'connect_string'
| {DATA | INDEX} DIRECTORY [=] 'absolute path to directory'
| DELAY_KEY_WRITE [=] {0 | 1}
| ENCRYPTION [=] {'Y' | 'N'}
| ENGINE [=] engine_name
| INSERT_METHOD [=] { NO | FIRST | LAST }
| KEY_BLOCK_SIZE [=] value
| MAX_ROWS [=] value
| MIN_ROWS [=] value
| PACK_KEYS [=] {0 | 1 | DEFAULT}
| PASSWORD [=] 'string'
| ROW_FORMAT [=] {DEFAULT | DYNAMIC | FIXED | COMPRESSED | REDUNDANT | COMPACT}
| STATS_AUTO_RECALC [=] {DEFAULT | 0 | 1}
| STATS_PERSISTENT [=] {DEFAULT | 0 | 1}
| STATS_SAMPLE_PAGES [=] value
| TABLESPACE tablespace_name [STORAGE {DISK | MEMORY}]
| UNION [=] (tbl_name[,tbl_name]...)
}
partition_options:
(see CREATE TABLE options)
2.1 修改表的存储引擎
语法:
-- 将非InnoDB存储引擎的表修改为 InnoDB存储引擎
ALTER TABLE t1 ENGINE = InnoDB;
测试记录:
mysql> create table t_5(id int,name varchar(100)) engine MyISAM;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> show create table t_5\G
*************************** 1. row ***************************
Table: t_5
Create Table: CREATE TABLE `t_5` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8
1 row in set (0.01 sec)
mysql> alter table t_5 engine InNODB;
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show create table t_5\G
*************************** 1. row ***************************
Table: t_5
Create Table: CREATE TABLE `t_5` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
2.2 修改表自增值
语法:
-- 修改表的自增列值
ALTER TABLE t1 AUTO_INCREMENT = 13;
测试记录:
mysql> create table t5(id int primary key auto_increment,name varchar(100));
Query OK, 0 rows affected (0.03 sec)
mysql> insert into t5(id,name) values (0,'abc');
Query OK, 1 row affected (0.01 sec)
mysql> select * from t5;
+----+------+
| id | name |
+----+------+
| 1 | abc |
+----+------+
1 row in set (0.00 sec)
mysql> alter table t5 auto_increment = 99;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> insert into t5(id,name) values (0,'abc');
Query OK, 1 row affected (0.01 sec)
mysql> select * from t5;
+----+------+
| id | name |
+----+------+
| 1 | abc |
| 99 | abc |
+----+------+
2 rows in set (0.00 sec)
-- 修改为比99小的10 居然没有报错
mysql> alter table t5 auto_increment = 10;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
-- 执行才知道 虽然修改语句没报错 但是木有生效
mysql> insert into t5(id,name) values (0,'abc');
Query OK, 1 row affected (0.01 sec)
mysql> select * from t5;
+-----+------+
| id | name |
+-----+------+
| 1 | abc |
| 99 | abc |
| 100 | abc |
+-----+------+
3 rows in set (0.00 sec)
2.3 修改表的字符集
语法:
-- 将表的字符集修改为utf8
ALTER TABLE t1 CHARACTER SET = utf8;
mysql> create table t6(id int,name varchar(100)) character set = utf8mb4;
Query OK, 0 rows affected (0.02 sec)
mysql> alter table t6 character set = utf8;
Query OK, 0 rows affected, 1 warning (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 1
2.4 修改表的备注信息
语法:
-- 修改表备注信息
ALTER TABLE t1 COMMENT = 'New table comment';
测试记录:
mysql> create table t7(id int,name varchar(100)) comment 'old comment';
Query OK, 0 rows affected (0.03 sec)
mysql> show create table t7\G
*************************** 1. row ***************************
Table: t7
Create Table: CREATE TABLE `t7` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='old comment'
1 row in set (0.00 sec)
mysql> alter table t7 comment = 'new comment';
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show create table t7\G
*************************** 1. row ***************************
Table: t7
Create Table: CREATE TABLE `t7` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='new comment'
1 row in set (0.00 sec)
2.5 重命名、重新定义和重新排序列
1.change
可以重命名或重定义列，或者两者一起
2.modify
修改列定义，但是不能修改列名
对于修改列定义而言，比change更方便
3.rename
可以重命名列，但是不能修改列的定义
对于重命名而言，比change更方便
语法:
-- 将列调整为非空
ALTER TABLE t1 MODIFY b INT NOT NULL;
-- 将列名由b修改为a
ALTER TABLE t1 RENAME COLUMN b TO a;
-- 修改col1列的定义
ALTER TABLE t1 MODIFY col1 BIGINT UNSIGNED DEFAULT 1 COMMENT 'my column';
测试记录:
mysql> create table t8(id int,name1 varchar(10));
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> alter table t8 modify id int not null;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table t8 rename column name1 to name;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> alter table t8 modify id bigint unsigned default 1 comment 'my column';
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql> show create table t8\G
*************************** 1. row ***************************
Table: t8
Create Table: CREATE TABLE `t8` (
`id` bigint unsigned DEFAULT '1' COMMENT 'my column',
`name` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql>
2.6 约束相关
`语法:
-- 删除主键约束
ALTER TABLE tbl_name DROP PRIMARY KEY;
-- 新增约束
ALTER TABLE tbl_name
ADD CONSTRAINT [symbol] CHECK (expr) [[NOT] ENFORCED];
-- 删除约束
ALTER TABLE tbl_name
DROP CONSTRAINT symbol;
ALTER TABLE tbl_name
DROP CHECK symbol;
测试记录:
mysql> create table t9(id int primary key,name1 varchar(10));
Query OK, 0 rows affected (0.02 sec)
mysql> show create table t9\G
*************************** 1. row ***************************
Table: t9
Create Table: CREATE TABLE `t9` (
`id` int NOT NULL,
`name1` varchar(10) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql>
mysql> alter table t9 drop primary key;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table t9 add unique u1(name1);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show create table t9\G
*************************** 1. row ***************************
Table: t9
Create Table: CREATE TABLE `t9` (
`id` int NOT NULL,
`name1` varchar(10) DEFAULT NULL,
UNIQUE KEY `u1` (`name1`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql> alter table t9 drop constraint u1;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
2.7 修改表和列的字符集
语法:
-- 修改表默认的字符集
ALTER TABLE tbl_name DEFAULT CHARACTER SET charset_name;
-- 修改列的字符集
ALTER TABLE t MODIFY latin1_text_col TEXT CHARACTER SET utf8;
测试记录:
mysql> create table t10(id int,name varchar(100));
Query OK, 0 rows affected (0.03 sec)
mysql> show create table t10\G
*************************** 1. row ***************************
Table: t10
Create Table: CREATE TABLE `t10` (
`id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql>
mysql>
mysql> alter table t10 default character set utf8mb4;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show create table t10\G
*************************** 1. row ***************************
Table: t10
Create Table: CREATE TABLE `t10` (
`id` int DEFAULT NULL,
`name` varchar(100) CHARACTER SET utf8 DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> alter table t10 modify name varchar(100) character set utf8;
Query OK, 0 rows affected, 1 warning (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 1
三.删除表
语法:
DROP [TEMPORARY] TABLE [IF EXISTS]
tbl_name [, tbl_name] ...
[RESTRICT | CASCADE]
测试记录:
mysql> drop table t1;
Query OK, 0 rows affected (0.02 sec)
mysql> drop table t11;
ERROR 1051 (42S02): Unknown table 'test1.t11'
mysql>
mysql>
mysql> drop table if exists t11;
Query OK, 0 rows affected, 1 warning (0.01 sec)
mysql>
mysql> show warnings;
+-------+------+---------------------------+
| Level | Code | Message |
+-------+------+---------------------------+
| Note | 1051 | Unknown table 'test1.t11' |
+-------+------+---------------------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> drop table t2,t3,t4,t5,t6,t7,t8,t9,t10;
Query OK, 0 rows affected (0.08 sec)