sql语句语法

1数据定义语句

    

1.1ALTER DATABASE语法

     

ALTER {DATABASE | SCHEMA} [db_name]
    alter_specification [, alter_specification] ...

alter_specification:
    [DEFAULT] CHARACTER SET charset_name
  | [DEFAULT] COLLATE collation_name

ALTER DATABASE用于更改数据库的全局特性。这些特性储存在数据库目录中的db.opt文件中。要使用ALTER DATABASE，您需要获得数据库ALTER权限。

CHARACTER SET子句用于更改默认的数据库字符集。COLLATE子句用于更改默认的数据库整序。

1.2alter table

ALTER [IGNORE] TABLE tbl_name alter_specification [, alter_specification] ...

alter_specification:
    ADD [COLUMN] column_definition [FIRST | AFTER col_name ]
  | ADD [COLUMN] (column_definition,...)
  | ADD INDEX [index_name] [index_type] (index_col_name,...)
  | ADD [CONSTRAINT [symbol]]
        PRIMARY KEY [index_type] (index_col_name,...)
  | ADD [CONSTRAINT [symbol]]
        UNIQUE [index_name] [index_type] (index_col_name,...)
  | ADD [FULLTEXT|SPATIAL] [index_name] (index_col_name,...)
  | ADD [CONSTRAINT [symbol]]
        FOREIGN KEY [index_name] (index_col_name,...)
        [reference_definition]
  | ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT}
  | CHANGE [COLUMN] old_col_name column_definition
        [FIRST|AFTER col_name]
  | MODIFY [COLUMN] column_definition [FIRST | AFTER col_name]
  | DROP [COLUMN] col_name
  | DROP PRIMARY KEY
  | DROP INDEX index_name
  | DROP FOREIGN KEY fk_symbol
  | DISABLE KEYS
  | ENABLE KEYS
  | RENAME [TO] new_tbl_name
  | ORDER BY col_name
  | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
  | [DEFAULT] CHARACTER SET charset_name [COLLATE collation_name]
  | DISCARD TABLESPACE
  | IMPORT TABLESPACE
  | table_options
  | partition_options
  | ADD PARTITION partition_definition
  | DROP PARTITION partition_names
  | COALESCE PARTITION number
  | REORGANIZE PARTITION partition_names INTO (partition_definitions)
  | ANALYZE PARTITION partition_names
  | CHECK PARTITION partition_names
  | OPTIMIZE PARTITION partition_names
  | REBUILD PARTITION partition_names
  | REPAIR PARTITION partition_names

  您可以使用CHANGE old_col_name column_definition子句对列进行重命名。重命名时，需给定旧的和新的列名称和列当前的类型。例如：要把一个INTEGER列的名称从a变更到b，您需要如下操作：

ALTER TABLE t1 CHANGE a b INTEGER;

如果您想要更改列的类型而不是名称， CHANGE语法仍然要求旧的和新的列名称，即使旧的和新的列名称是一样的。例如：

ALTER TABLE t1 CHANGE b b BIGINT NOT NULL;

您也可以使用MODIFY来改变列的类型，此时不需要重命名：

ALTER TABLE t1 MODIFY b BIGINT NOT NULL;

1.3create database

CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name

    [create_specification [, create_specification] ...]

create_specification:

    [DEFAULT] CHARACTER SET charset_name

  | [DEFAULT] COLLATE collation_name

1.4 create index

CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name

    [USING index_type]

    ON tbl_name (index_col_name,...)

index_col_name:

    col_name [(length)] [ASC | DESC]

1.5create table

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 [)];

1.6drop database

DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

1.7drop index

DROP INDEX index_name ON tbl_name

1.8drop table

DROP [TEMPORARY] TABLE [IF EXISTS]

    tbl_name [, tbl_name] ...

    [RESTRICT | CASCADE]

1.9RENAME TABLE

RENAME TABLE tbl_name TO new_tbl_name

    [, tbl_name2 TO new_tbl_name2] ...

2数据操作语句

1.delete

单表语法：

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name

    [WHERE where_definition]

    [ORDER BY ...]

    [LIMIT row_count]

多表语法：

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]

    tbl_name[.*] [, tbl_name[.*] ...]

    FROM table_references

    [WHERE where_definition]

或：

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]

    FROM tbl_name[.*] [, tbl_name[.*] ...]

    USING table_references

    [WHERE where_definition]

2do

DO expr [, expr] ...

DO用于执行表达式，但是不返回任何结果。DO是SELECT expr的简化表达方式。DO有一个优势，就是如果您不太关心结果的话，DO的速度稍快。

DO主要用于执行有副作用的函数，比如RELEASE_LOCK()。

3.HANDLER语法

HANDLER tbl_name OPEN [ AS alias ]
HANDLER tbl_name READ index_name { = | >= | <= | < } (value1,value2,...)
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ index_name { FIRST | NEXT | PREV | LAST }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ { FIRST | NEXT }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name CLOSE

HANDLER语句提供通往表存储引擎接口的直接通道。HANDLER可以用于MyISAM和InnoDB表。

HANDLER...OPEN语句用于打开一个表，通过后续的HANDLER...READ语句建立读取表的通道。本表目标不会被其它线程共享，也不会关闭，直到线程调用HANDLER...CLOSE或线程中止时为止。如果您使用一个别名打开表，则使用其它HANDLER语句进一步参阅表是必须使用此别名，而不能使用表名。

这个语句是根据索引读取表中的数据。

HANDLER比SELECT更快：

       一个指定的存储引擎管理程序目标为了HANDLER...OPEN进行整序。该目标被重新用于该表的后续的HANDLER语句；不需要对每个语句进行重新初始化。

     涉及的分析较少。

     没有优化程序或查询校验开销。

    在两个管理程序请求之间，不需要锁定表。

     管理程序接口不需要提供外观一致的数据（例如，允许无条理的读取），所以存储引擎可以使用优化，而SELECT通常不允许使用优化。

4.insert

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]

    [INTO] tbl_name [(col_name,...)]

    VALUES ({expr | DEFAULT},...),(...),...

    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

或：

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]

    [INTO] tbl_name

    SET col_name={expr | DEFAULT}, ...

    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

或：

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]

    [INTO] tbl_name [(col_name,...)]

    SELECT ...

    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

5 LOAD DATA INFILE

LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name.txt'

    [REPLACE | IGNORE]

    INTO TABLE tbl_name

    [FIELDS

        [TERMINATED BY 'string']

        [[OPTIONALLY] ENCLOSED BY 'char']

        [ESCAPED BY 'char' ]

    ]

    [LINES

        [STARTING BY 'string']

        [TERMINATED BY 'string']

    ]

    [IGNORE number LINES]

    [(col_name_or_user_var,...)]

    [SET col_name = expr,...)]

6replace

REPLACE [LOW_PRIORITY | DELAYED]

    [INTO] tbl_name [(col_name,...)]

    VALUES ({expr | DEFAULT},...),(...),...

或：

REPLACE [LOW_PRIORITY | DELAYED]

    [INTO] tbl_name

    SET col_name={expr | DEFAULT}, ...

或：

REPLACE [LOW_PRIORITY | DELAYED]

    [INTO] tbl_name [(col_name,...)]

    SELECT ...

       REPLACE的运行与INSERT很相像。只有一点除外，如果表中的一个旧记录与一个用于PRIMARY KEY或一个UNIQUE索引的新记录具有相同的值，则在新记录被插入之前，旧记录被删除。

       注意，除非表有一个PRIMARY KEY或UNIQUE索引，否则，使用一个REPLACE语句没有意义。该语句会与INSERT相同，因为没有索引被用于确定是否新行复制了其它的行。

7select

SELECT

    [ALL | DISTINCT | DISTINCTROW ]

      [HIGH_PRIORITY]

      [STRAIGHT_JOIN]

      [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]

      [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]

    select_expr, ...

    [INTO OUTFILE 'file_name' export_options

      | INTO DUMPFILE 'file_name']

    [FROM table_references

    [WHERE where_definition]

    [GROUP BY {col_name | expr | position}

      [ASC | DESC], ... [WITH ROLLUP]]

    [HAVING where_definition]

    [ORDER BY {col_name | expr | position}

      [ASC | DESC] , ...]

    [LIMIT {[offset,] row_count | row_count OFFSET offset}]

    [PROCEDURE procedure_name(argument_list)]

    [FOR UPDATE | LOCK IN SHARE MODE]]

join:

table_references: table_reference [, table_reference] …

table_reference:
    table_factor
  | join_table table_factor:
    tbl_name [[AS] alias]
        [{USE|IGNORE|FORCE} INDEX (key_list)]
  | ( table_references )
  | { OJ table_reference LEFT OUTER JOIN table_reference
        ON conditional_expr }

join_table:
    table_reference [INNER | CROSS] JOIN table_factor [join_condition]
  | table_reference STRAIGHT_JOIN table_factor
  | table_reference STRAIGHT_JOIN table_factor ON condition
  | table_reference LEFT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [LEFT [OUTER]] JOIN table_factor
  | table_reference RIGHT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [RIGHT [OUTER]] JOIN table_factor join_condition:
    ON conditional_expr
  | USING (column_list)

union:

SELECT ...

UNION [ALL | DISTINCT]

SELECT ...

[UNION [ALL | DISTINCT]

SELECT ...]

8.subquery

8.1子查询作为标量操作数

CREATE TABLE t1 (s1 INT, s2 CHAR(5) NOT NULL);

INSERT INTO t1 VALUES(100, 'abcde');

SELECT (SELECT s2 FROM t1);

8.2使用子查询进行比较

SELECT column1 FROM t1

WHERE column1 = (SELECT MAX(column2) FROM t2);

8.3使用ANY, IN和SOME进行子查询

SELECT s1 FROM t1 WHERE s1 > ANY (SELECT s1 FROM t2);

SELECT s1 FROM t1 WHERE s1 IN    (SELECT s1 FROM t2);

4行子查询

SELECT * FROM t1 WHERE (1,2) = (SELECT column1, column2 FROM t2);
SELECT * FROM t1 WHERE ROW(1,2) = (SELECT column1, column2 FROM t2);

5.EXISTS和NOT EXISTS

SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2);

哪些种类的商店出现在一个或多个城市里？

                SELECT DISTINCT store_type FROM stores

                  WHERE EXISTS (SELECT * FROM cities_stores

                                WHERE cities_stores.store_type = stores.store_type);

 哪些种类的商店没有出现在任何城市里？

               SELECT DISTINCT store_type FROM stores

                  WHERE NOT EXISTS (SELECT * FROM cities_stores

                                    WHERE cities_stores.store_type = stores.store_type);

哪些种类的商店出现在所有城市里？

                SELECT DISTINCT store_type FROM stores s1

                  WHERE NOT EXISTS (

                    SELECT * FROM cities WHERE NOT EXISTS (

                      SELECT * FROM cities_stores

                       WHERE cities_stores.city = cities.city

                       AND cities_stores.store_type = stores.store_type));

6.关联子查询

SELECT * FROM t1 WHERE column1 = ANY

(SELECT column1 FROM t2 WHERE t2.column2 = t1.column2);

7.from子句中的子查询

SELECT sb1,sb2,sb3

FROM (SELECT s1 AS sb1, s2 AS sb2, s3*2 AS sb3 FROM t1) AS sb

WHERE sb1 > 1;

结果：2, '2', 4.0。

8 truncate

TRUNCATE [TABLE] tbl_name

TRUNCATE TABLE与DELETE FROM有以下几处不同：

         删减操作会取消并重新创建表，这比一行一行的删除行要快很多。

         删减操作不能保证对事务是安全的；在进行事务处理和表锁定的过程中尝试进行删减，会发生错误。

        被删除的行的数目没有被返回。

       只要表定义文件tbl_name.frm是合法的，则可以使用TRUNCATE TABLE把表重新创建为一个空表，即使数据或索引文件已经被破坏。        

       表管理程序不记得最后被使用的AUTO_INCREMENT值，但是会从头开始计数。即使对于MyISAM和InnoDB也是如此。MyISAM和InnoDB通常不再次使用序列值。

       当被用于带分区的表时，TRUNCATE TABLE会保留分区；即，数据和索引文件被取消并重新创建，同时分区定义（.par）文件不受影响。

9.update

Single-table语法：

UPDATE [LOW_PRIORITY] [IGNORE] tbl_name

    SET col_name1=expr1 [, col_name2=expr2 ...]

    [WHERE where_definition]

    [ORDER BY ...]

    [LIMIT row_count]

Multiple-table语法：

UPDATE [LOW_PRIORITY] [IGNORE] table_references

    SET col_name1=expr1 [, col_name2=expr2 ...]

    [WHERE where_definition]