在MYSQL中创建表的方法有哪些?

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name

[(create_definition,...)]

[table_options] [select_statement]

或：

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name

[(] LIKE old_tbl_name [)]

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:

col_name type [NOT NULL | NULL] [DEFAULT default_value]

[AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]

[COMMENT 'string'] [reference_definition]

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

index_col_name:

col_name [(length)] [ASC | DESC]

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

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 }

| DATA 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]

[ SUBPARTITION BY

[LINEAR] HASH(expr)

| [LINEAR] KEY(column_list)

[SUBPARTITIONS(num)]

]

[(partition_definition), [(partition_definition)], ...]

partition_definition:

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_definition), [(subpartition_definition)], ...]

subpartition_definition:

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)

建表过程就是一个画表头的过程（声明字段过程）

存储同样的数据，不同的lie类型所占的空间和效率是不一样的，这就是我们建表前要列类型的意义

所以，列类型的存储与占据的字节关系是学习的重点

一般而言，设某类型N字节

N字节，8N位

0 -->2^8N-1

-2^(8N-1) --->2^(8N-1)-1

对于int类型：占的字节越多，存储的范围也越大

添加一个学分 列

alter table class add score tinyint unsigned not null default 0

(M)unsigned zerofill

zerofill: zero是零，fill是填充，代表0填充

M表示补0宽度，即位数不够，用0填充没有补齐的宽度，并不改变其大小

M必须和zerofill配合才有意义

用zerofill表示属性，则该属性也默认为unsigned类型

char、varchar分别称为定长、变长类型

char(100)是存储0~100个长度

varchar(100)也是存储0~100个长度

char为定长，当输入长度不足设定的长度时，会用空格去补，而取出来时，会将空格去掉，所以，用concat连接时，char的空格被自动删除了

【注】char(M),varchar(M)限制的是字符，不是字节

即char(2) charset utf8, 储存2 个utf8字符，比如中国

utf8一个字符占3个字节

一般用来存储文章内容、新闻内容等

声明text时，不必使用默认值

所以不必加上 not null default '' ,而是直接使用 artice text

用来存储图像、音频等二进制信息

意义：blob防止因为字符集的问题，导致信息丢失

比如一张图中有0xFF字节，这个在ASCII字符集默认 非法，在入库的时候，被过滤了

超出范围，year类型只占1字节，最多能存256种变化

范围：1901~2155

year能简写成两位，但不推荐这样写（但现在的版本不支持了）

---