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  • 精妙Sql语句

    1.  判断a表中有而b表中没有的记录

    select a.* from tbl1 a

    left join tbl2 b

    on a.key = b.key

    where b.key is null

             虽然使用in也可以实现,但是这种方法的效率更高一些

    2.  新建一个与某个表相同结构的表

    select * into b

    from a where 1<>1

    3between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

    4. 说明:包括所有在 TableA 中但不在 TableBTableC 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)

    5. 初始化表,可以将自增长表的字增长字段置为1

    TRUNCATE TABLE table1

    6.多语言设置数据库或者表或者order by的排序规则

             --修改用户数据库的排序规则

    ater database dbname collate SQL_Latin1_General_CP1_CI_AS

    --修改字段的排序规则

    alter table a alter column c2 varchar(50) collate SQL_Latin1_General_CP1_CI_AS

    --按姓氏笔画排序

    select * from 表名 order by 列名 Collate Chinese_PRC_Stroke_ci_as

    --按拼音首字母排序

    select * from 表名 order by 列名 Collate Chinese_PRC_CS_AS_KS_WS

    7.列出所有的用户数据表:

    SELECT TOP 100 PERCENT o.name AS 表名

    FROM dbo.syscolumns c INNER JOIN

          dbo.sysobjects o ON o.id = c.id AND objectproperty(o.id, N'IsUserTable') = 1 AND

          o.name <> 'dtproperties' LEFT OUTER JOIN

          dbo.sysproperties m ON m.id = o.id AND m.smallid = c.colorder

    WHERE (c.colid = 1)

    ORDER BY o.name, c.colid

     

    8.列出所有的用户数据表及其字段信息:

    SELECT TOP 100 PERCENT c.colid AS 序号, o.name AS 表名, c.name AS 列名,

          t.name AS 类型, c.length AS 长度, c.isnullable AS 允许空,

          CAST(m.[value] AS Varchar(100)) AS 说明

    FROM dbo.syscolumns c INNER JOIN

          dbo.sysobjects o ON o.id = c.id AND objectproperty(o.id, N'IsUserTable') = 1 AND

          o.name <> 'dtproperties' INNER JOIN

          dbo.systypes t ON t.xusertype = c.xusertype LEFT OUTER JOIN

          dbo.sysproperties m ON m.id = o.id AND m.smallid = c.colorder

    ORDER BY o.name, c.colid

    9Leftright Join的另外一种简洁的写法

    select * from a,b where a.id *= b.id  --*= 相当于 LEFT JOIN 

    select * from a,b where a.id =* b.id  --=* 相当于 Right JOIN 

    10Update from delete from

    11.得到表中最小的未使用的ID

             SELECT (CASE WHEN EXISTS(SELECT * FROM Handle b WHERE b.HandleID = 1)

    THEN MIN(HandleID) + 1 ELSE 1 END) as HandleID

    FROM Handle

    WHERE NOT HandleID IN (SELECT a.HandleID - 1 FROM Handle a)

    12.随机取得记录

             SELECT TOP 10 * FROM T1 ORDER BY NEWID()

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  • 原文地址:https://www.cnblogs.com/yukaizhao/p/essential_sql.html
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