mysql DROP DATABASE删除数据库与创建数据库create database

DROP DATABASE [IF EXISTS] db_name
DROP DATABASE 移除数据库是的所有表并删除数据库。如果你在一个符号链接(symbolic link)数据库上执行一个 DROP DATABASE，链接与原始数据库均会被删除。要非常小心地使用这个命令！

DROP DATABASE 返回从数据库目录下删除的文件数目。通常，它是表的数目的三倍，因为第张表通常对应于一个 “.MYD” 文件、一个 “.MYI” 文件和一个 “.frm” 文件。

DROP DATABASE 命令从给定的数据库目录下移除以下列为扩展名的所有文件：

扩展名扩展名扩展名 Ext
.BAK .DAT .HSH .ISD
.ISM .ISM .MRG .MYD
.MYI .db .frm

所有包含两个数字的子目录(RAID 目录)也同样被删除。

在 MySQL 3.22 或以后的版本中，你可以使用关键词 IF EXISTS 以防止如果数据库不存在时发生错误。

你也可以使用 mysqladmin 移除数据库。查看章节 4.8 MySQL 客户端脚本和实用程序。

6.5.3 CREATE TABLE 句法

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

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
LIKE old_table_name;

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    FULLTEXT [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,...)

index_col_name:
col_name [(length)]

reference_definition:
        REFERENCES tbl_name [(index_col_name,...)]
                   [MATCH FULL | MATCH PARTIAL]
                   [ON DELETE reference_option]
                   [ON UPDATE reference_option]

reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT

table_options:
TYPE = {BDB | HEAP | ISAM | InnoDB | MERGE | MRG_MYISAM
                | MYISAM }
or AUTO_INCREMENT = #
or AVG_ROW_LENGTH = #
or CHECKSUM = {0 | 1}
or COMMENT = "string"
or MAX_ROWS = #
or MIN_ROWS = #
or PACK_KEYS = {0 | 1 | DEFAULT}
or PASSWORD = "string"
or DELAY_KEY_WRITE = {0 | 1}
or      ROW_FORMAT= { default | dynamic | fixed | compressed }
or RAID_TYPE= {1 | STRIPED | RAID0 } RAID_CHUNKS=#
                    RAID_CHUNKSIZE=#
or UNION = (table_name,[table_name...])
or INSERT_METHOD= {NO | FIRST | LAST }
or      DATA DIRECTORY="absolute path to directory"
or      INDEX DIRECTORY="absolute path to directory"

select_statement:
[IGNORE | REPLACE] SELECT ... (Some legal select statement)
CREATE TABLE 以给定的名字在当前数据库创建一个表。允许的表名规则在章节 6.1.2 数据库、表、索引、列和别名中被给出。如果没有当前数据库或表已经存在，一个错误将会发生。

补充：数据库,mysql教程