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MySQL 组合键怎么写?一个表有2列 - colA 和 colB, 他们都不是唯一的, 但是组合起来是唯一的, 请问SQL语句怎么写, 谢谢
MySQL 组合键怎么写?一个表有2列 - colA 和 colB, 他们都不是唯一的, 但是组合起来是唯一的, 请问SQL语句怎么写, 谢谢
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colA int,
colB int,
colC int,
primary key(colA,colB)
);
13.1.5.1. 沉寂的列规格变更
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)
· PRIMARY KEY可以是一个多列索引。但是,在列规约中使用PRIMARY KEY关键字属性无法创建多列索引。这么做只能把一个列标记为主列。您必须使用一个单独的PRIMARY KEY(index_col_name, ...)子句。
====>
create table tb(
colA int,
colB int,
colC int,
unique key(colA,colB) --或者primary key(colA,colB)
);