常用sql语句

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标签:sql语句

SQL 常用语句积累:

一、 SQL 基本语句

SQL 分类:

DDL —数据定义语言 (Create , Alter , Drop , DECLARE)

DML —数据操纵语言 (Select , Delete , Update , Insert)

DCL —数据控制语言 (GRANT , REVOKE , COMMIT , ROLLBACK)

 

首先 , 简要介绍基础语句:

1 、说明:创建数据库

Create DATABASE database-name

2 、说明:删除数据库

drop database dbname

3 、说明:备份 sql server

---  创建 备份数据的  device

USE master

EXEC sp_addumpdevice ‘disk‘, ‘testBack‘, ‘c:\mssql7backup\MyNwind_1.dat‘

---  开始 备份

BACKUP DATABASE pubs TO testBack

4 、说明:创建新表

create table tabname(col1 type1 [not null] [primary key],col2 type2 [not null],..)

根据已有的表创建新表:

A : create table tab_new like tab_old ( 使用旧表创建新表 )

B : create table tab_new as select col1,col2 …  from tab_old definition only

5 、说明:删除新表 drop table tabname

6 、说明:增加一个列

Alter table tabname add column col type

注:列增加后将不能删除。 DB2 中列加上后数据类型也不能改变,唯一能改变的是增加 varchar 类型的长度。

7 、说明:添加主键:  Alter table tabname add primary key(col)

说明:删除主键:  Alter table tabname drop primary key(col)

8 、说明:创建索引: create [unique] index idxname on tabname(col … .)

删除索引: drop index idxname

注:索引是不可更改的,想更改必须删除重新建。

9 、说明:创建视图: create view viewname as select statement

删除视图: drop view viewname

10 、说明:几个简单的基本的 sql 语句

选择: select * from table1 where  范围

插入: insert into table1(field1,field2) values(value1,value2)

删除: delete from table1 where  范围

更新: update table1 set field1=value1 where  范围

查找: select * from table1 where field1 like  ’ %value1% ’  ---like 的语法很精妙,查资料 !

排序: select * from table1 order by field1,field2 [desc]

总数: select count * as totalcount from table1

求和: select sum(field1) as sumvalue from table1

平均: select avg(field1) as avgvalue from table1

最大: select max(field1) as maxvalue from table1

最小: select min(field1) as minvalue from table1

11 、说明:几个高级查询运算词

A :  UNION  运算符

UNION  运算符通过组合其他两个结果表(例如  TABLE1  和  TABLE2 )并消去表中任何重复行而派生出一个结果表。当  ALL  随 UNION  一起使用时(即  UNION ALL ),不消除重复行。两种情况下,派生表的每一行不是来自  TABLE1  就是来自  TABLE2 。

B :  EXCEPT  运算符

EXCEPT  运算符通过包括所有在  TABLE1  中但不在  TABLE2  中的行并消除所有重复行而派生出一个结果表。当  ALL  随  EXCEPT  一起使用时 (EXCEPT ALL) ,不消除重复行。

C :  INTERSECT  运算符

INTERSECT  运算符通过只包括  TABLE1  和  TABLE2  中都有的行并消除所有重复行而派生出一个结果表。当  ALL  随  INTERSECT 一起使用时 (INTERSECT ALL) ,不消除重复行。

注:使用运算词的几个查询结果行必须是一致的。

12 、说明:使用外连接

A 、 left outer join :

左外连接(左连接):结果集几包括连接表的匹配行,也包括左连接表的所有行。

SQL: select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c

B : right outer join:

右外连接 ( 右连接 ) :结果集既包括连接表的匹配连接行,也包括右连接表的所有行。

C : full outer join :

全外连接:不仅包括符号连接表的匹配行,还包括两个连接表中的所有记录。

二、 SQL 子查询语句

      1 、单行子查询

        select ename,deptno,sal

        from emp

        where deptno=(select deptno from dept where loc=‘NEW YORK‘) ;

     2 、多行子查询

        SELECT ename,job,sal

        FROM EMP

        WHERE deptno in ( SELECT deptno FROM dept WHERE dname LIKE ‘A%‘) ;

     3 、多列子查询

        SELECT deptno,ename,job,sal

        FROM EMP

        WHERE (deptno,sal) IN (SELECT deptno,MAX(sal) FROM EMP GROUP BY deptno) ;

     4 、内联视图子查询

       (1)SELECT ename,job,sal,rownum

          FROM (SELECT ename,job,sal FROM EMP ORDER BY sal) ;

       (2)SELECT ename,job,sal,rownum

          FROM ( SELECT ename,job,sal FROM EMP ORDER BY sal)

          WHERE rownum<=5 ;

 

     5 、在 HAVING 子句中使用子查询

        SELECT deptno,job,AVG(sal) FROM EMP GROUP BY deptno,job HAVING AVG(sal)>(SELECT sal FROM EMP WHERE ename=‘MARTIN‘) ;

     6 、内连接   左连接   右连接举例;

     select sys_user.user_id ,sys_user.user_code  from  sys_user inner join XZFW_BANJIE onsys_user.user_id=XZFW_BANJIE.userid

    小例子:

     select top 10 * from sys_user  where user_code not in (select  user_code  from sys_user where user_code like ‘%yzj%‘)

     select top 2 * from (select top 2 *  from td.users order by us_username desc) users order by us_username desc

     7 、删除约束语句:

     alter   table   dbo.XZFW_SYS_USER   drop   CONSTRAINT  FK1772E1891324F678

      8 、记录数查询

      select count(user_pass) from sys_user

      select count(*) from sys_user where user_code!=‘admin‘

      9 、在范围之间取值 ( between ... and .. 用法 )

      select sys_user.user_id,sys_user.user_name,xzfw_shoujian.caseid from sys_user inner join xzfw_shoujian on sys_user.user_id=xzfw_shoujian.userid where user_id between 5 and 100

      或 select * from sys_user  where user_id<10 and user_id>1

      10 、 三表查询实例:(三张表为: USER_DETAILS , Subject , Score )

select USER_DETAILS.USER_NAME,Subject.SubjectName,Score.Score from USER_DETAILS inner join Scoreon USER_DETAILS.USER_ID=Score.USER_ID inner join Subject on Score.SubjectID=Subject.SubjectIDwhere USER_DETAILS.USER_ID=1

  常用查询举例:

 

select * from dbo.USER_DETAILS where USER_NAME=‘Cheers Li‘ and USER_POSITION=‘SQE‘

select * from dbo.USER_DEPT

select * from dbo.USER_DETAILS

select top 3* from dbo.USER_DETAILS inner join dbo.USER_DEPT onUSER_DETAILS.USER_DEPT_ID=dbo.USER_DEPT.USER_DEPT_ID

insert into dbo.USER_DEPT (USER_DEPT_ID,USER_DEPT_NAME)values(‘QE_01‘,‘Software quality engineer‘)

update USER_DEPT set USER_DEPT_ID=‘QE_02‘ where USER_DEPT_NAME=‘Quality Control‘

delete from dbo.USER_DEPT where USER_DEPT_ID=‘QE_01‘

select dbo.USER_DETAILS.USER_NAME,dbo.USER_DETAILS.USER_AGE,dbo.USER_DEPT.USER_DEPT_NAME,USER_DEPT.USER_DEPT_ID fromdbo.USER_DETAILS right join dbo.USER_DEPT onUSER_DETAILS.USER_DEPT_ID=dbo.USER_DEPT.USER_DEPT_ID

select count(USER_NAME)from dbo.USER_DETAILS where USER_NAME=‘Cheers Li‘

alter table USER_DEPT add Testcolumn char

alter table USER_DEPT drop column Testcolumn

select top 3* from(select top 3* from dbo.USER_DETAILS where USER_DEPT_ID=‘DEV_01‘ order byUSER_AGE desc)aa order by USER_ID desc

 

select * from dbo.USER_DETAILS where USER_NAME=(select max(USER_NAME) fromdbo.USER_DETAILS)

三、补充常用语句。

1. select employees.employee_id,employees.first_name,employees.last_name,salary*(1+0.1) new_salary from hr.employees;

2. select employee_id,first_name from hr.employees where first_name like ‘B%‘;

3. select count(*) from hr.employees where first_name like ‘B%‘;

4. select job_id,avg(salary),sum(salary),max(salary),count(*) from hr.employees group by job_id;


 

其次,大家来看一些不错的 sql 语句

1 、说明:复制表 ( 只复制结构 , 源表名: a 新表名: b) (Access 可用 )

法一: select * into b from a where 1<>1

法二: select top 0 * into b from a

 

2 、说明:拷贝表 ( 拷贝数据 , 源表名: a 目标表名: b) (Access 可用 )

insert into b(a, b, c) select d,e,f from b;

 

3 、说明:跨数据库之间表的拷贝 ( 具体数据使用绝对路径 ) (Access 可用 )

insert into b(a, b, c) select d,e,f from b in ‘具体数据库’ where 条件

例子: ..from b in ‘"&Server.MapPath(".")&"\data.mdb" &"‘ where..

 

4 、说明:子查询 ( 表名 1 : a 表名 2 : b)

select a,b,c from a where a IN (select d from b ) 或者 : select a,b,c from a where a IN (1,2,3)

 

5 、说明:显示文章、提交人和最后回复时间

select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b

 

6 、说明:外连接查询 ( 表名 1 : a 表名 2 : b)

select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c

 

7 、说明:在线视图查询 ( 表名 1 : a )

select * from (Select a,b,c FROM a) T where t.a > 1;

 

8 、说明: between 的用法 ,between 限制查询数据范围时包括了边界值 ,not between 不包括

select * from table1 where time between time1 and time2

select a,b,c, from table1 where a not between 数值 1 and 数值 2

 

9 、说明: in 的使用方法

select * from table1 where a [not] in ( ‘值 1 ’ , ’值 2 ’ , ’值 4 ’ , ’值 6 ’ )

 

10 、说明:两张关联表,删除主表中已经在副表中没有的信息

delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1 )

 

11 、说明:四表联查问题:

select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c inner join d on a.a=d.d where .....

 

12 、说明:日程安排提前五分钟提醒

SQL: select * from 日程安排 where datediff(‘minute‘,f 开始时间 ,getdate())>5

 

13 、说明:一条 sql 语句搞定数据库分页

select top 10 b.* from (select top 20 主键字段 , 排序字段 from 表名 order by 排序字段 desc) a, 表名 b where b. 主键字段 = a. 主键字段 order by a. 排序字段

 

14 、说明:前 10 条记录

select top 10 * form table1 where 范围

 

15 、说明:选择在每一组 b 值相同的数据中对应的 a 最大的记录的所有信息 ( 类似这样的用法可以用于论坛每月排行榜 , 每月热销产品分析 , 按科目成绩排名 , 等等 .)

select a,b,c from tablename ta where a=(select max(a) from tablename tb where tb.b=ta.b)

 

16 、说明:包括所有在 TableA 中但不在 TableB 和 TableC 中的行并消除所有重复行而派生出一个结果表

(select a from tableA ) except (select a from tableB) except (select a from tableC)

 

17 、说明:随机取出 10 条数据

select top 10 * from tablename order by newid()

 

18 、说明:随机选择记录

select newid()

 

19 、说明:删除重复记录

Delete from tablename where id not in (select max(id) from tablename group by col1,col2,...)

 

20 、说明:列出数据库里所有的表名

select name from sysobjects where type=‘U‘

 

21 、说明:列出表里的所有的

select name from syscolumns where id=object_id(‘TableName‘)

 

22 、说明:列示 type 、 vender 、 pcs 字段,以 type 字段排列, case 可以方便地实现多重选择,类似 select 中的 case 。

select type,sum(case vender when ‘A‘ then pcs else 0 end),sum(case vender when ‘C‘ then pcs else 0 end),sum(case vender when ‘B‘ then pcs else 0 end) FROM tablename group by type

显示结果:

type vender pcs

电脑 A 1

电脑 A 1

光盘 B 2

光盘 A 2

手机 B 3

手机 C 3

 

23 、说明:初始化表 table1

TRUNCATE TABLE table1

 

24 、说明:选择从 10 到 15 的记录

select top 5 * from (select top 15 * from table order by id asc) table_ 别名 order by id desc


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