SQL 精妙语句（确实牛！）

SQL 精妙语句（确实牛！）
Posted on 2005-07-17 00:02陈朋奕 阅读(860)评论(7)  编辑 收藏引用收藏至365Key 所属分类:MySQL资料翻译
如何从一位菜鸟蜕变成为高手，灵活使用的SQL语句是必不可少的。本文收集了部分比较经典，常用的SQL语句供大家参考，希望对大家有所帮助。
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‘) ¦¦ ‘/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)
Feedback
# re: SQL 精妙语句（确实牛！）  回复
2005-07-19 15:41 by胡阳
select * into b from a where 1<>1
我怎么用不来呀
显示
ERROR 1327 (42000): Undeclared variable: b
如果能用那真是太好了
# re: SQL 精妙语句（确实牛！）  回复
2005-07-26 04:56 by于行义
假设表a,ID字段为id,"得到表中最小的未使用的ID号"貌似这样写更简单(可能效率会低点)
select min(id+1) from (select id from a)as a1 where id not in(select id-1 from a)
# re: SQL 精妙语句（确实牛！）  回复
2005-07-27 16:40 by
回复：
select * into b from a where 1<>1
我怎么用不来呀
显示
ERROR 1327 (42000): Undeclared variable: b
如果能用那真是太好了
我在MYSQL中如下试用成功：
create table b as select * from a where 1<>1
请试一下
# re: SQL 精妙语句（确实牛！）  回复
2005-07-27 23:30 by
才看到……
呵呵，胡兄弟少了Create语句
于兄弟的SQL应该用得比我好，这是转载的，不过其实这里sql的子查询语句只是为了获得原表的结构，如果需要的只是某些列也可以将*改为那些列的名字。
复制表的某些列也可以使用这样的方法：
create table b as select a.id, a.name, a.address from user a;
# re: SQL 精妙语句（确实牛！）  回复
2005-07-29 07:29 by于行义
还是你写的那个是对的......我这个少算了一种情况......
手比脑子动作的快,肯定是会出错的,汗........
select min(id+1) from a where id not in(select id-1 from a);
这样子大多数情况都适用,但是唯独当缺失的ID为1的时候,不适用了.会返回"除1以外最小的缺失ID",而不返回1.
所以单独判断一下子这个id=1是不是存在,就是你上面说的那种办法了...
select (case when exists(select id from a where id=1) then min(id+1) else 1 end) from a where id not in(select id-1 from a);
现在看来,这种方法应该是最优的办法了,就MySQL-4.1.x来说.
# re: SQL 精妙语句（确实牛！）  回复
2005-07-30 00:11 by
看来于大哥是个SQL高手，呵呵，对SQL的理解很深刻
给了另一种解法，让小弟开了眼界
只是我觉得这样做的话会加大SQL的开销，似乎没有必要。
有个问题请教，假设我现在有两个表，表结构一样，但里面有些数据不一样，如果我想要将这两个表中不一样的部分输出到第三个表中，怎么写SQL？
# re: SQL 精妙语句（确实牛！）  回复
2005-07-30 06:46 by于行义
假设表a,b,c,均有字段val,把a和b中不一样的部分输入到c中,似乎可以这样做:
b里面有a里面没有的-->输入进c:
insert into c(val) select val from a where val not in (select val from b);
a里面有b里面没有的-->输入进c:
insert into c(val) select val from b where val not in (select val from a);
合起来大概是这样:
insert into c(val) select val from a where val not in (select val from b) union select val from b where val not in (select val from a);