|
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',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 *
FROM studentinfo
WHERE NOT EXISTS
(SELECT * FROM student
WHERE studentinfo.Fid = student.Fid)
AND 系名称='XXXX' and 专业名称='XXXX'
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~~~~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 newfield2.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
|
