create_definition:
col_name type [NOT NULL | NULL] [DEFAULT default_value] [AUTO_INCREMENT]
[PRIMARY KEY] [reference_definition]
or PRIMARY KEY (index_col_name,...)
or KEY [index_name] (index_col_name,...)
or INDEX [index_name] (index_col_name,...)
or UNIQUE [INDEX] [index_name] (index_col_name,...)
or [CONSTRAINT symbol] FOREIGN KEY index_name (index_col_name,...)
[reference_definition]
or CHECK (expr)
type:
TINYINT[(length)] [UNSIGNED] [ZEROFILL]
or SMALLINT[(length)] [UNSIGNED] [ZEROFILL]
or MEDIUMINT[(length)] [UNSIGNED] [ZEROFILL]
or INT[(length)] [UNSIGNED] [ZEROFILL]
or INTEGER[(length)] [UNSIGNED] [ZEROFILL]
or BIGINT[(length)] [UNSIGNED] [ZEROFILL]
or REAL[(length,decimals)] [UNSIGNED] [ZEROFILL]
or DOUBLE[(length,decimals)] [UNSIGNED] [ZEROFILL]
or FLOAT[(length,decimals)] [UNSIGNED] [ZEROFILL]
or DECIMAL(length,decimals) [UNSIGNED] [ZEROFILL]
or NUMERIC(length,decimals) [UNSIGNED] [ZEROFILL]
or CHAR(length) [BINARY]
or VARCHAR(length) [BINARY]
or DATE
or TIME
or TIMESTAMP
or DATETIME
or TINYBLOB
or BLOB
or MEDIUMBLOB
or LONGBLOB
or TINYTEXT
or TEXT
or MEDIUMTEXT
or LONGTEXT
or ENUM(value1,value2,value3,...)
or SET(value1,value2,value3,...)
ALTER TABLE句法
ALTER [IGNORE] TABLE tbl_name alter_spec [, alter_spec ...]
alter_specification:
ADD [COLUMN] create_definition [FIRST | AFTER column_name ]
or ADD INDEX [index_name] (index_col_name,...)
or ADD PRIMARY KEY (index_col_name,...)
or ADD UNIQUE [index_name] (index_col_name,...)
or ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT}
or CHANGE [COLUMN] old_col_name create_definition
or MODIFY [COLUMN] create_definition
or DROP [COLUMN] col_name
or DROP PRIMARY KEY
or DROP INDEX index_name
or RENAME [AS] new_tbl_name
or table_options
ALTER TABLE允许你修改一个现有表的结构 ,你可以增加或删除列、创造或消去索引、改变现有列的类型、或重新命名列或表本身。你也能改变表的注释和表的类型