MySQL (一) 数据库定义语言(DDL) CREATE/DROP/ALTER

18 June 2015

第一: 创建CREATE

1 创建数据库/模式: CREATE DATABASE/SCHEME 语法

Syntax:
    create {database | schema} [IF NOT EXISTS] db_name
        [create_specification [, create_specification] ...];

    create_specification 选项:
        [DEFAULT] CHARACTER SET charset_name |
        [DEFAULT] COLLATE collation_name;

    # 栗子:
    1. create database blog;
    2. create database if not exist blog;
    3. create database blog;
        default character set utf8;
    4. create database if not exists blog
        default character set utf8;
    5. create schema blog
        default character set utf8;

2 创建索引: CREATE INDEX 语法

Syntax:
    CREATE [UNIQUE | FULLTEXTISPATIAL] INDEX index_name
        [USING index_type]
        ON tbl_name (index_col_name);
    
    index_col_name 选项:
        col_name [(length)] [ASC | DESC];

    # 栗子
    # show databses;
    # create database if not exist t;
    # use t;
    # show tables;
    # create table t (a int primary key auto_increment, b varchar(255));
    # desc table_name;
    create index t_index 
        on t (a desc, b);

3 创建表: CREATE TABLE 语法

// Syntax
    CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
        [(create_defination, ...)]
        [table_option] [select_statement];
或
    CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
        [(] LIKE old_tbl_name [)];

create_defination:
    column_defination 
    | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name, ...)
    | KEY [index_name] [index_type] (index_col_name, ...)
    | INDEX [index_name] [index_type] (index_col_name, ...)
    | [CONSTRAINT [symbol]] UNIQUE [index]
        [index_name] [index_type] (index_col_name, ...)
    | [FULLTEXTISPATIAL] [INDEX] [index_name] (index_col_name, ...)
    | [CONSTRAINT [symbol]] FOREIGN KEY
        [index_name] (index_col_name, ...) [reference_definition]
    | CHECK (expr)

column_defination:
    col_name type [NOT NULL | NULL] [DEFAULT default_value]
        [AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
        [COMMET 'string'] [reference_defination]

type:
      TINYINT(length)       [UNSIGNED] [ZEROFILL]
    | SMALLINT[(length)]    [UNSIGNED] [ZEROFILL]
    | MEDIUMINT[(length)]   [UNSIGNED] [ZEROFILL]
    | INT[(length)]         [UNSIGNED] [ZEROFILL]
    | INTEGER[(length)]     [UNSIGNED] [ZEROFILL]
    | BIGINT[(length)]      [UNSIGNED] [ZEROFILL]
    | REAL[(length, decimals)]      [UNSIGNED] [ZEROFILL]
    | DOUBLE[(length, decimals)]    [UNSIGNED] [ZEROFILL]
    | FLOAT[(length, decimals)]     [UNSIGNED] [ZEROFILL]
    | DECIMAL(length, decimals)     [UNSIGNED] [ZEROFILL]
    | NUMERIC(length, decimals)     [UNSIGNED] [ZEROFILL]
    | DATE
    | TIME
    | TIMESTAMP
    | DATETIME
    | CHAR(length) [BINARY | ASCII | UNICODE]
    | VARCHAR(length) [BINARY]
    | TINYBLOB
    | BLOB
    | MEDIUMBLOB
    | LONGBLOB
    | TINYTEXT [BINARY]
    | TEXT [BINARY]
    | MEDIUMTEXT [BINARY]
    | LONGTEXT [BINARY]
    | ENUM(value1, vaule2, value3, ...)
    | SET(value1, value2, value3, ...)
    | spatial_type

index_of_col_name:
    col_name [(length)] [ASC | DESC]

reference_defination:
    REFERENCES tbl_name [(index_col_name)]
        [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
        [ON DELETE reference_option]
        [ON UPDATE reference_option]

reference_option:
    RESTRICT | CASCADE | SET NULL | NO ACTION

table_options:
    table_option [table_option] ...

table_option:
      {ENGINE | TYPE} = engine_name
    | AUTO_INCREMENT = value
    | AVG_ROW_LENGTH = value
    | [DEFAULT] CHARACTER SET charset_name [COLLATE collation_name]
    | CHECKSUM = {0 | 1}
    | COMMENT = 'string'
    | CONNECTION = 'connect_string'
    | MAX_ROWS = value
    | MIN_ROWS = value
    | PACK_KEYS = {0 | 1 | DEFAULT}
    | PASSWORD = 'string'
    | DELAY_KEY_WRITE = {0 | 1}
    | ROW_FORMAT = {DEFAULT | DYNAMIC | FIXED | COMPRESSED | REDUNDANT | COMPACT}
    | UNION = (tbl_name[, tbl_name, ...])
    | INSERT_METHOD = {NO, FIRST, LAST}
    | DATE DIRECTORY = 'absolute path to directory'
    | INDEX DIRECTORY = 'absolute path to directory'

partition_options:
    PARTITION BY
          [LINEAR] HASH(expr)
        | [LINEAR] KEY(column_list)
        | RANGE(expr)
        | LIST(column_list)
    [PARTITIONS num]
    [ SUNPARTITION BY
          [LINEAR] HASH(expr)
        | [LINEAR] KEY(column_list)
      [SUBPARTITIONS(num)]
    ]
    [(partition_defination) [, partition_defination, ...]]

partition_defination:
    PARTITION partition_name
        [VALUES {
            LESS THAN (expr) | MAXVALUE | IN (value_list)
            }]
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'comment_text']
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] (tablespace_name)]
        [NODEGROUP [=] node_group_id]
        [(subpartition_defination) [, (subpartition_defination), ...]]

subpartition_defination:
    SUBPARTITION logical_name
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'comment_text']
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] (tablespace_name)]
        [NODEGROUP [=] node_group_id]

select_statement:
    [IGNORE | REPLACE] [AS] SELECT ... (some legal select statement)

// CREATE TABLE 栗子
// 1. 最简单
create table Student
(
    sno int,
    sname varchar(10),
    cno int
);

// 2. INF: 原子性(主属性不为空NULL) + 主键(PRIMARY key) 
create table Student
(
    id int primary key auto_increment,
    sname varchar(10) not null,
    cname varchar(30) not null
);

// 3. 不存在才创建
create table if no exists Cost
(
    id int,
    money decimal(20, 2),
    date date,
    time timestamp,
    comment text,
    age integer(2),
    primary key (id)
);

// 4. 外键/外码: foreign key .... references ...
create table SC
(
    id int,
    sno int,
    primary key (id),
    foreign key (sno) references Student(sno)
);
desc SC;
show create table SC;

// 5. 临时TABLE, 退出后自动删除
create temporary table temp_table 
(
    ...
);

一、数据定义语言:

第一: 删除DROP

1 DROP DATABASE 语法
- DROP {DATABASE | SCHENA} [IF EXISTS] db_name
2 DROP INDEX 语法
- DROP INDEX index_name ON tbl_name
3 DROP TABLE 语法
- DROP [TEMPRARY] TABLE [IF EXISTS] tbl_name[, tbl_name, ...] [RESTRICT | CASCADE]

第二: 改变结构ALTER

1 ALTER DATABASE 语法

Syntax:
    ALTER {DATABASE | SCHEMA} [db_name]
        alter_specification [, alter_specification, ...]

    alter_specification:
          [DEFAULT] CHARACTER SET charset_name
        | [DEFAULT] COLLATE collation_name

2 ALTER TABLE 语法

Syntax:
    ALTER [IGNORE] TABLE tbl_name
        alter_specification [, alter_specification, ...]

    alter_specification:
          ADD [COLUMN] column_defination [FIRST | LAST | FIFTH | BEFORE col_name | AFTER col_name]
        | ADD [COLUMN] (column_defination, ...)
        | ADD INDEX [index_name] [index_type] (index_col_name, ...)
        | ADD [CONSTRAINT [symbol]]
            PROMARY KEY [index_name] [index_type] (index_col_name, ...)
        | ADD [CONSTRAINT [symbol]]
            UNIQUE [index_name] [index_type] (index_col_name, ...)
        | ADD [FULLTEXTISPATIAL] [index_name] (index_col_name, ...)
        | ADD [CONSTRAINT [symbol]]
            FOREIGN KEY [index_name] (index_col_name, ...)
            [reference_defination]
        | ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT}
        | CHANGE [COLUMN] old_col_name column_defination
        | MODIFY [COLUMN] column_defination [FIRST | AFTER col_name]
        | DROP [COLUMN] col_name
        | DROP PRIMARY KEY
        | DROP INDEX index_name
        | DROP FOREIGN KEY fk_symbol
        | DISABLE KEYS
        | ENABLE KEYS
        | RENAME [TO] new_tbl_name
        | ORDER BY col_name
        | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
        | [DEFAULT] CHARACTER SET charset_name [COLLATE collation_name]
        | DISCADE TABLESPACE
        | IMPORT TABLESPACE
        | table_options
        | partition_options
        | ADD PARTITION partition_defination
        | DROP PARTITION partition_names
        | COALESCE PARTITION number
        | REORGANIZE PARTITION partition_names INTO (partition_definations)
        | ANALYZE PARTITION partition_names
        | CHECK PARTITION partition_names
        | OPTIMIZE PARTITION partition_names
        | REBUILD PARTITION partition_names
        | REPAIR PARTITION partition_names

2 ALTER 栗子

-- 1. 加入主键:
    alter table Student
        add primary key (Sno);
    /* desc Student; */
    /* show create table Student; */

-- 2. 加入新列:
    alter table Student
        add column Sdept varchar(2);

-- 3. 外键(含外键的是子表，被外键的是父表， 父表必须有主键)
    alter table SC
        add foreign key (Sno) references Student(Sno);

-- 4. 添加按顺序的列,默认是最后(LAST):
    -- FIRST: 加到第一列
    -- SENCOND: 加到第二咧
    -- THIRD: 加到第三列
    -- AFTER column_name: 在column_name列之后一列
    -- BEFORE column_name: 在column_name列之前一列
    -- 栗子:
    alter table Student
        add column id int first;
    alter table Student
        add column Sname varchar(20) before Sdept;
    alter table Student
        add column sex varchar(1) after Sname;
    show create table Student;

-- 5. 改变列名及属性(一起): CHANGE
    -- 1. 重命名, 最好RENAME
    alter table Student
        change column sex Ssex varchar(1);
    -- 2. 只修改属性, 用MODIFY效果更佳
    alter table Student
        change column Sname Sname varchar(30);

-- 6. 修正仅属性: MODIFY
    alter table Student
        modify column Sname varchar(255);
    show create table Student;

-- 7. 删除列:
    alter table Student
        drop column first_name;
    desc Student;

-- 8. 删除主键PRIMARY KEY:
    alter table Student
        drop primary key;

-- 9. 删除外键FOREIGN KEY: 
    -- 要拿到CONSTRAINT_NAME
        -- 1 show create table Student;
        -- 2 自己命名的限制名
    alter table Student
        drop foreign key Student_ibfk_1; -- 这里限制名是自动生成的
        /* 限制名可以自己在定义或添加属性时指定 */

-- 10. 删除索引INDEX:
    alter table Student
        drop index index_name;

-- 11. 重命名表名:
    alter table Student
        rename to student;
    show tables;
    另一种办法:
        rename table student to Student;

原文链接大专栏 https://www.dazhuanlan.com/2019/08/16/5d560a639e7b1/

来源：https://www.cnblogs.com/chinatrump/p/11416299.html

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