MYSQL语法速查之表创建

校招笔试数据库，发现忘得差不多了，发篇博文纪念一下……!

数据库无非就是各种二维表的操作，先看列定义。
定义一个列最主要的还是指定了列中元素的数据类型，和相关的操作。

列定义

column_definition:
    col_name type [NOT NULL | NULL] [DEFAULT default_value][AUTO_INCREMENT] [UNIQUE | PRIMARY KEY] [reference_definition]

[NOT NULL | NULL] 指定是否能为空，
[DEFAULT default_value]指定默认值，
[AUTO_INCREMENT]指定自增长，
[UNIQUE | PRIMARY KEY]不重复或者是主键，
[reference_definition] 外键

reference_definition:
    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

[ON DELETE CASCADE] 级联删除

表定义

掌握 references tal_name cascade
掌握了列定义，表定义也很简单！
表定义

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options] [select_statement]


create_definition:
    column_definition
  | [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,...)
  | [FULLTEXT|SPATIAL] [INDEX] [index_name] (index_col_name,...)
  | [CONSTRAINT [symbol]] FOREIGN KEY
        [index_name] (index_col_name,...) [reference_definition]
  | CHECK (expr)

column_definition之后基本上都是对列的一些约束信息。
[CONSTRAINT [symbol]] 设置一个约束，symbol是约束名，
掌握常用的 primary key 和 foreign key 定义。

最后看一下数据类型

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,value2,value3,...)
  | SET(value1,value2,value3,...)
  | spatial_type