数据库笔记

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 a; 


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 


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：列出表里的所有的列 
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 


declare @a varchar(100),@b varchar(20) 
select @a='abcdefbcmnbcde',@b='bc' 
select (len(@a)-len(replace(@a,@b,'')))/len(@b)


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)


一年中所有为星期二的日期 


select dateadd(day,x,col),'星期二' from 
( 
select cast('2006-1-1' as datetime) as col 
)a cross join 
( 
SELECT  top 365 b8.i+b7.i + b6.i + b5.i + b4.i +b3.i +b2.i + b1.i + b0.i x 
FROM(SELECT 0 i UNION ALL SELECT 1) b0 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 2) b1 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 4) b2 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 8) b3 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 16) b4 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 32) b5 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 64) b6 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 128) b7 
CROSS JOIN(SELECT 0 i UNION ALL SELECT 256) b8 
order by 1 
)b 
where datepart(dw,dateadd(day,x,col))=3


实现将整型123456789转换为123，456，789
SELECT REPLACE(CONVERT(varchar, CONVERT(money, 123456789), 1), '.00', '')


复制表结构，而不复制内容 




select * into #table1 
from admin 
where 1 <>1 --不会复制数据 


select * from #table1 


drop table #table1 


这样#table1就有了admin 的所有字段


select 字段1,字段3 into newtable where 1<>1


--查询当前表的数据量计数
select max(a.rowcnt)  计数
from sysindexes a
join sys.objects b on b.object_id=a.id
where b.[name]='kucun'


--查询当前数据库的数据量计数，按表分组
use --数据库
select max(a.rowcnt) 计数,b.[name] 表名 
from sysindexes a
join sys.objects b on b.object_id=a.id
where b.type='U'
group by b.[name]
having max(a.rowcnt) >0
order by 1 desc


速度查询数据条数
select rowcnt from sysindexes where id=object_id('表名') 


取得一个表的所有字段名，用逗号分割开。。
DECLARE @columns VARCHAR(500);


SELECT
    @columns=isnull(@columns+',','')+name
FROM syscolumns
WHERE [id]=OBJECT_ID(N'表名');


SELECT @columns


SELECT [rows]
FROM sysindexes
WHERE (id = OBJECT_ID('GENERALDATA')) AND (indid < 2)//速度查询行数
 
select count(1) from table//速度查询行数




N-M条记录
1.
select top m * into 临时表(或表变量) from tablename order by columnname -- 将top m笔插入
set rowcount n
select * from 表变量 order by columnname desc




2.
select top n * from 
(select top m * from tablename order by columnname) a
order by columnname desc




3.
如果tablename里没有其他identity列，那么：
select identity(int) id0,* into #temp from tablename


取n到m条的语句为：
select * from #temp where id0 >=n and id0 <= m


如果你在执行select identity(int) id0,* into #temp from tablename这条语句的时候报错,那是因为你的DB中间的select into/bulkcopy属性没有打开要先执行：
exec sp_dboption 你的DB名字,'select into/bulkcopy',true




4.
如果表里有identity属性，那么简单：
select * from tablename where identitycol between n and m


计算一个库里各个表的记录总数：
select b.name,a.rowcnt from sysindexes a,sysobjects b 
where a.id=b.id and a.indid<2 and b.xtype='u'


--统计数据库里每个表的详细情况
   EXEC sp_MSforeachtable @command1="sp_spaceused '?'"


   --获得每个表的记录数和容量:
   EXEC sp_MSforeachtable @command1="print '?'",
        @command2="sp_spaceused '?'",
        @command3= "SELECT count(*) FROM ? "






select
    o.name as tbname,
    c.name as columnname,
    t.name as typename,
    c.max_length
from sys.tables as o
    join sys.columns as c
on o.object_id=c.object_id
    join sys.types as t
on c.system_type_id=t.system_type_id








  SELECT
        C.column_id
        ,C.name
        ,type    = T.name + CASE T.user_type_id WHEN 41 THEN '('+CAST(C.scale AS VARCHAR) +')'    -- time
            WHEN 42 THEN '('+CAST(C.scale AS VARCHAR) +')'                                        -- datetime2
            WHEN 43 THEN '('+CAST(C.scale AS VARCHAR) +')'                                        -- datetimeoffset
            WHEN 106 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'    -- decimal
            WHEN 108 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'    -- numeric
            WHEN 165 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- varbinary
            WHEN 167 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- varchar
            WHEN 173 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- binary
            WHEN 175 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- char
            WHEN 231 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- nvarchar
            WHEN 239 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'        -- nchar
            ELSE ''
            END
        ,C.is_identity
        ,C.is_nullable
        ,DefaultText = ISNULL(STUFF(LEFT(D.definition,LEN(D.definition)-1),1,1,''),'')
    FROM sys.columns C
    INNER JOIN sys.types T ON C.user_type_id = T.user_type_id 
    LEFT JOIN sys.default_constraints D ON D.[object_id] =C.default_object_id 
        AND D.parent_object_id = C.[object_id] AND D.parent_column_id = C.column_id 
    WHERE C.[object_id] = OBJECT_ID('你的表名');

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