整理了一些SQL数据库技巧

时间:2022-12-29 18:01:46
 

蛙蛙推荐:整理了一些SQL数据库技巧,贴一下

一.怎样删除一个表中某个字段重复的列呀,举个例子
表[table1]
id    name
1 aa
2 bb
3 cc
1 aa
2 bb
3 cc
我想最后的表是这样的
id    name
1 aa
2 bb
3 cc
回答:
将记录存到临时表#t中,重复的记录只存一条,然后将临时表#t中的记录再存回原表中,注意“select distinct id,class,name”要包含你需要的所有字段,否则有些字段就被删掉了。
在查询管理器里执行下面代码:
-----------------------------
SELECT DISTINCT id,, name
INTO #t
FROM table1 DELETE table1
          INSERT
        INTO table1
                  SELECT *
                FROM #t
------------------------------
二.找出既会VB又会PHP的人
表是这样的:
ID 员工 技能
1 1 VB
2 1 PHP
3 1 ASP
4 2 PHP
5 3 ASP
6 4 VB
7 4 ASP
要从这张表中找出既会VB又会PHP的人,SQL该怎么写啊?
回答:
---------------------------------------------------------------------------------------------
SELECT 员工 FROM [Table] WHERE 员工 IN(SELECT 员工 FROM [Table] WHERE 技能='VB' ) AND 技能='PHP'
----------------------------------------------------------------------------------------------
三.数据库合并问题
access里的两个表,想让两个表的内容合并

表[a]结构如下:
[id]        编号        自动编号
[name]      名称        文本
[price]     价格        数字
[guige]     规格        文本
[changjia]  生产厂家    文本
[baozhuang] 包装        文本
[danwei]    单位        文本
共有900条记录,除了id和name字段,其他均可以为空

表[b]结构如下:
[id]        编号        自动编号
[name]      名称        文本
[price]     价格        数字
[changjia]  生产厂家    文本
[danwei]    单位        文本
[xingzhi]   性质        文本
共有800条记录,除了id和name字段,比表[a]少几个字段,但还多一个[xingzhi]的字符安其它均可以为空

现在想生成一个新表[c],结构如下,而且内容是两个表的内容之和,
[id]        编号        自动编号
[name]      名称        文本
[price]     价格        数字
[guige]     规格        文本
[changjia]  生产厂家    文本
[baozhuang] 包装        文本
[danwei]    单位        文本
[xingzhi]   性质        文本

用sql语句也可以,手工操作也好,xml也好,别管怎么着吧,怎么实现呀,哥们要郁闷坏了,真要让我们再输入800条记录,我就挂了,
回答:
1.这样
-----------------------------
insert into c(id,name,.....)
select id,name,.....
from a
insert into c(id,name,.....)
select max(id)+1,name,.....
from b
------------------------------
2.更正:
如果直接在查询分析器里执行:
-------------------------------
insert into c(name,.....)
select name,.....
from a
insert into c(name,.....)
select name,.....
from b
--------------------------------
3.用union方法
---------------------------------
insert into [c] ([id] ,编号,自动编号)
select [id],编号,自动编号 from [a]
union
select [id],编号,自动编号 from [b]
-----------------------------------
4.asp的解决办法
------------------------------------------------------------
<% '循环检测a表
Set rs = Server.CreateObect("ADODB.RECORDSET")
      rs.open "select * from a order by id",conn,1,1
      Do while not rs.eof
          Call actAdd(rs("name"))    '调用像b表添加内容的函数!
      rs.MoveNext
      Loop
rs.Close
Set rs = Nothing

Sub actAdd(txt)
Dim ts, sql
sql = "insert into b(name) values('"& txt &"')"
Set ts = Conn.Execute(sql)
      ts.Close
Set ts = Nothing
end Sub
%>
------------------------------------------------------------------
5.asp的解决办法
-----------------------------------------------------------------------------------
<%
dim arr_temp1,arr_temp2,arr_data
set rs=conn.execute("select id,name,price,guige,changjia,baozhuang,danwei from a")
arr_temp1=rs.getrows
rs.close
set rs=nothing

set rs=conn.execute("select id,name,price,guige,changjia,danwei,xingzhi from b")
arr_temp2=rs.getrows
rs.close
set rs=nothing

rem 开始处理
redim arr_data(ubound(arr_temp1,2)+ubound(arr_temp2,2),7)
rem 把两个数组的内容复制进来
这一部分自己写了做两个循环
然后再存进数据库
%>
---------------------------------------------------------------------------------------
最后转一些经典的SQL语句:
1.蛙蛙推荐:一些精妙的SQL语句
-----------------------------------------------------------------------------------------------------------------------
说明:复制表(只复制结构,源表名:a 新表名:b)

SQL: select * into b from a where 1<>1

 

说明:拷贝表(拷贝数据,源表名:a 目标表名:b)

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

 

说明:显示文章、提交人和最后回复时间

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

 

说明:外连接查询(表名1:a 表名2:b)

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

 

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

 

 

说明:两张关联表,删除主表中已经在副表中没有的信息

SQL: 

delete from info where not exists ( select * from infobz where info.infid=infobz.infid )

 

说明:--

SQL: 

SELECT A.NUM, A.NAME, B.UPD_DATE, B.PREV_UPD_DATE

  FROM TABLE1,

    (SELECT X.NUM, X.UPD_DATE, Y.UPD_DATE PREV_UPD_DATE

        FROM (SELECT NUM, UPD_DATE, INBOUND_QTY, STOCK_ONHAND

                FROM TABLE2

              WHERE TO_CHAR(UPD_DATE,'YYYY/MM') = TO_CHAR(SYSDATE, 'YYYY/MM')) X,

            (SELECT NUM, UPD_DATE, STOCK_ONHAND

                FROM TABLE2

              WHERE TO_CHAR(UPD_DATE,'YYYY/MM') =

                    TO_CHAR(TO_DATE(TO_CHAR(SYSDATE, 'YYYY/MM') &brvbar;&brvbar; '/01','YYYY/MM/DD') - 1, 'YYYY/MM') ) Y,

        WHERE X.NUM = Y.NUM (+)

          AND X.INBOUND_QTY + NVL(Y.STOCK_ONHAND,0) <> X.STOCK_ONHAND ) B

WHERE A.NUM = B.NUM

 

说明:--

SQL: 

select * from studentinfo where not exists(select * from student where studentinfo.id=student.id) and 系名称='"&strdepartmentname&"' and 专业名称='"&strprofessionname&"' order by 性别,生源地,高考总成绩

 

说明:

从数据库中去一年的各单位电话费统计(电话费定额贺电化肥清单两个表来源)

SQL:

SELECT a.userper, a.tel, a.standfee, TO_CHAR(a.telfeedate, 'yyyy') AS telyear,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '01', a.factration)) AS JAN,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '02', a.factration)) AS FRI,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '03', a.factration)) AS MAR,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '04', a.factration)) AS APR,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '05', a.factration)) AS MAY,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '06', a.factration)) AS JUE,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '07', a.factration)) AS JUL,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '08', a.factration)) AS AGU,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '09', a.factration)) AS SEP,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '10', a.factration)) AS OCT,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '11', a.factration)) AS NOV,

      SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '12', a.factration)) AS DEC

FROM (SELECT a.userper, a.tel, a.standfee, b.telfeedate, b.factration

        FROM TELFEESTAND a, TELFEE b

        WHERE a.tel = b.telfax) a

GROUP BY a.userper, a.tel, a.standfee, TO_CHAR(a.telfeedate, 'yyyy')

 

说明:四表联查问题:

SQL: 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 .....

 

说明:得到表中最小的未使用的ID号

SQL:

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)
-----------------------------------------------------------------------------------------------------------------------
2.删除重复数据
-----------------------------------------------------------------------------------------------------------------------
一、具有主键的情况
a.具有唯一性的字段id(为唯一主键)
delete table
where id not in
(
select max(id) from table group by col1,col2,col3...
)
group by 子句后跟的字段就是你用来判断重复的条件,如只有col1,
那么只要col1字段内容相同即表示记录相同。

b.具有联合主键
假设col1+','+col2+','...col5 为联合主键
select * from  table where col1+','+col2+','...col5 in (
  select max(col1+','+col2+','...col5) from table
where having count(*)>1
group by col1,col2,col3,col4
)
group by 子句后跟的字段就是你用来判断重复的条件,
如只有col1,那么只要col1字段内容相同即表示记录相同。

c:判断所有的字段
  select * into #aa from table group by id1,id2,....
  delete table
  insert into table
  select * from #aa

二、没有主键的情况

a:用临时表实现
select identity(int,1,1) as id,* into #temp from ta
delete #temp
where id not in
(
  select max(id) from # group by col1,col2,col3...
)
delete table ta
inset into ta(...)
   select ..... from #temp

b:用改变表结构(加一个唯一字段)来实现
alter table 表 add  newfield int identity(1,1)
delete 表
where newfield not in
(
select min(newfield) from 表 group by 除newfield外的所有字段
)

alter table 表 drop column newfield
-----------------------------------------------------------------------------------------------------------------------