精妙SQL语句 值得推敲

zhengjialon

在其它网站看到的，感觉值得推荐：



精妙SQL语句 值得推敲



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)



数据库里有多条同名记录。

读取出来的时候，相同的就显示一条的方法：



select distinct `field` from table



field就唯一不会重复了



选出出现频率最大的值，例如

CELL_ID DATE TIME BUSY_TCH_MEAN

30151 2003-12-20 0:00:00 0.01

30151 2003-12-20 1:00:00 1.89

30151 2003-12-20 2:00:00 0.59

30151 2003-12-20 3:00:00 0.43

30151 2003-12-20 4:00:00 0.7

30151 2003-12-20 5:00:00 0.01

30151 2003-12-20 6:00:00 0.08

30151 2003-12-20 7:00:00 0.01

30151 2003-12-20 8:00:00 1.2

30151 2003-12-20 9:00:00 1.57

30151 2003-12-20 10:00:00 3.96

30151 2003-12-20 11:00:00 3.96

30151 2003-12-20 12:00:00 5.65

其中BUSY_TCH_MEAN字段出现频率最多的值是0.01，怎么把他找出来（用SQL）？





SELECT `BUSY_TCH_MEAN` , COUNT(*) AS num

FROM mytable

GROUP BY `BUSY_TCH_MEAN`

ORDER BY num DESC

LIMIT 0,1

kunlun

顶一下

goodidea

非常不错\！

顺便补充一下SELECT `BUSY_TCH_MEAN` , COUNT(*) AS num

FROM mytable

GROUP BY `BUSY_TCH_MEAN`

ORDER BY num DESC

LIMIT 0,1这种格式的SQL语句不被JET支持，MySQL中常见

MS的产品用SELECT TOP 1  `BUSY_TCH_MEAN` , COUNT(*) AS num

FROM mytable

GROUP BY `BUSY_TCH_MEAN`

ORDER BY num DESC

duzili

收藏！

zyp

珍藏[em17][em17][em17][em17][em17][em17][em17]

lzx-shmily

很好!下來學習學習。

中国人

收藏

esnake

select * into b from a where 1<>1
改为如此:select * into b from a where false

wxj131

学习一下.