SELECT * FROM Customers DELETE FROM Customers WHERE PKId=1 UPDATE Customers SET UserID='sq' WHERE PKId=1 INSERT INTO Customers(UserID,TrueName) VALUES ('shiqiang','宝剑')
在oracle8.05中设置访问数据库别名: WSTXNY.WORLD = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.252)(PORT = 1521)) (CONNECT_DATA = (SID = WSTXNY)) )
表4.1 比较运算符
名称 | 实例 |
=(等于) | select * from scott.emp where job=’MANAGER’; |
select * from scott.emp where sal=1100; | |
!= (不等于) | select * from scott.emp where job!=’MANAGER’; |
select * from scott.emp where sal!=1100; | |
^=(不等于) | select * from scott.emp where job^=’MANAGER’; |
select * from scott.emp where sal^=1100; | |
<>(不等于) | select * from scott.emp where job<>’MANAGER’; |
select * from scott.emp where sal<>1100; | |
<(小于) | select * from scott.emp where sal<2000; |
select * from scott.emp where job<’MANAGER’; | |
>(大于) | select * from scott.emp where sal>2000; |
select * from scott.emp where job>’MANAGER’; | |
<=(小于等于) | select * from scott.emp where sal<=2000; |
select * from scott.emp where job<=’MANAGER’; | |
>=(大于等于) | select * from scott.emp where sal>=2000; |
select * from scott.emp where job>=’MANAGER’; | |
in(列表) | select * from scott.emp where sal in (2000,1000,3000); |
select * from scott.emp where job in (’MANAGER’,’CLERK’); | |
not in(不在列表) | select * from scott.emp where sal not in (2000,1000,3000); |
select * from scott.emp where job not in (’MANAGER’,’CLERK’); | |
between(介于之间) | select * from scott.emp where sal between 2000 and 3000; |
select * from scott.emp where job between ’MANAGER’ and ’CLERK’; | |
not between (不介于之间) | select * from scott.emp where sal not between 2000 and 3000; |
select * from scott.emp where job not between ’MANAGER’ and ’CLERK’; | |
like(模式匹配) | select * from scott.emp where job like ’M%’; |
select * from scott.emp where job like ’M__’; | |
not like (模式不匹配) | select * from scott.emp where job not like ’M%’; |
select * from scott.emp where job not like ’M__’; | |
Is null (是否为空) | select * from scott.emp where sal is null; |
select * from scott.emp where job is null; | |
is not null(是否为空) | select * from scott.emp where sal is not null; |
select * from scott.emp where job is not null; |
SQLServer和Oracle常用函数对比 数学函数 1.绝对值 S:select abs(-1) value O:select abs(-1) value from dual
2.取整(大) S:select ceiling(-1.001) value O:select ceil(-1.001) value from dual
3.取整(小) S:select floor(-1.001) value O:select floor(-1.001) value from dual
4.取整(截取) S:select cast(-1.002 as int) value O:select trunc(-1.002) value from dual
5.四舍五入 S:select round(1.23456,4) value 1.23460 O:select round(1.23456,4) value from dual 1.2346
6.e为底的幂 S:select Exp(1) value 2.7182818284590451 O:select Exp(1) value from dual 2.71828182
7.取e为底的对数 S:select log(2.7182818284590451) value 1 O:select ln(2.7182818284590451) value from dual; 1
8.取10为底对数 S:select log10(10) value 1 O:select log(10,10) value from dual; 1
9.取平方 S:select SQUARE(4) value 16 O:select power(4,2) value from dual 16
10.取平方根 S:select SQRT(4) value 2 O:select SQRT(4) value from dual 2
11.求任意数为底的幂 S:select power(3,4) value 81 O:select power(3,4) value from dual 81
12.取随机数 S:select rand() value O:select sys.dbms_random.value(0,1) value from dual;
13.取符号 S:select sign(-8) value -1 O:select sign(-8) value from dual -1
14.圆周率 S:SELECT PI() value 3.1415926535897931 O:不知道
15.sin,cos,tan 参数都以弧度为单位 例如:select sin(PI()/2) value 得到1(SQLServer)
16.Asin,Acos,Atan,Atan2 返回弧度
17.弧度角度互换(SQLServer,Oracle不知道) DEGREES:弧度-〉角度 RADIANS:角度-〉弧度
数值间比较
18. 求集合最大值 S:select max(value) value from (select 1 value union select -2 value union select 4 value union select 3 value)a
O:select greatest(1,-2,4,3) value from dual
19. 求集合最小值 S:select min(value) value from (select 1 value union select -2 value union select 4 value union select 3 value)a
O:select least(1,-2,4,3) value from dual
20.如何处理null值(F2中的null以10代替) S:select F1,IsNull(F2,10) value from Tbl O:select F1,nvl(F2,10) value from Tbl
21.求字符序号 S:select ascii('a') value O:select ascii('a') value from dual
22.从序号求字符 S:select char(97) value O:select chr(97) value from dual
23.连接 S:select '11'+'22'+'33' value O:select CONCAT('11','22') 33 value from dual
23.子串位置 --返回3 S:select CHARINDEX('s','sdsq',2) value O:select INSTR('sdsq','s',2) value from dual
23.模糊子串的位置 --返回2,参数去掉中间%则返回7 S:select patindex('%d%q%','sdsfasdqe') value O:oracle没发现,但是instr可以通过第四个参数控制出现次数 select INSTR('sdsfasdqe','sd',1,2) value from dual 返回6
24.求子串 S:select substring('abcd',2,2) value O:select substr('abcd',2,2) value from dual
25.子串代替 返回aijklmnef S:SELECT STUFF('abcdef', 2, 3, 'ijklmn') value O:SELECT Replace('abcdef', 'bcd', 'ijklmn') value from dual
26.子串全部替换 S:没发现 O:select Translate('fasdbfasegas','fa','我' ) value from dual
27.长度 S:len,datalength O:length
28.大小写转换 lower,upper
29.单词首字母大写 S:没发现 O:select INITCAP('abcd dsaf df') value from dual
30.左补空格(LPAD的第一个参数为空格则同space函数) S:select space(10)+'abcd' value O:select LPAD('abcd',14) value from dual
31.右补空格(RPAD的第一个参数为空格则同space函数) S:select 'abcd'+space(10) value O:select RPAD('abcd',14) value from dual
32.删除空格 S:ltrim,rtrim O:ltrim,rtrim,trim
33. 重复字符串 S:select REPLICATE('abcd',2) value O:没发现
34.发音相似性比较(这两个单词返回值一样,发音相同) S:SELECT SOUNDEX ('Smith'), SOUNDEX ('Smythe') O:SELECT SOUNDEX ('Smith'), SOUNDEX ('Smythe') from dual SQLServer中用SELECT DIFFERENCE('Smithers', 'Smythers') 比较soundex的差 返回0-4,4为同音,1最高
日期函数 35.系统时间 S:select getdate() value O:select sysdate value from dual
36.前后几日 直接与整数相加减
37.求日期 S:select convert(char(10),getdate(),20) value O:select trunc(sysdate) value from dual select to_char(sysdate,'yyyy-mm-dd') value from dual
38.求时间 S:select convert(char(8),getdate(),108) value O:select to_char(sysdate,'hh24:mm:ss') value from dual
39.取日期时间的其他部分 S:DATEPART 和 DATENAME 函数 (第一个参数决定) O:to_char函数 第二个参数决定
参数---------------------------------下表需要补充 year yy, yyyy quarter qq, q (季度) month mm, m (m O无效) dayofyear dy, y (O表星期) day dd, d (d O无效) week wk, ww (wk O无效) weekday dw (O不清楚) Hour hh,hh12,hh24 (hh12,hh24 S无效) minute mi, n (n O无效) second ss, s (s O无效) millisecond ms (O无效) ----------------------------------------------
40.当月最后一天 S:不知道 O:select LAST_DAY(sysdate) value from dual
41.本星期的某一天(比如星期日) S:不知道 O:SELECT Next_day(sysdate,7) vaule FROM DUAL;
42.字符串转时间 S:可以直接转或者select cast('2004-09-08'as datetime) value O:SELECT To_date('2004-01-05 22:09:38','yyyy-mm-dd hh24-mi-ss') vaule FROM DUAL;
43.求两日期某一部分的差(比如秒) S:select datediff(ss,getdate(),getdate()+12.3) value O:直接用两个日期相减(比如d1-d2=12.3) SELECT (d1-d2)*24*60*60 vaule FROM DUAL;
44.根据差值求新的日期(比如分钟) S:select dateadd(mi,8,getdate()) value O:SELECT sysdate+8/60/24 vaule FROM DUAL;
45.求不同时区时间 S:不知道 O:SELECT New_time(sysdate,'ydt','gmt' ) vaule FROM DUAL;
-----时区参数,北京在东8区应该是Ydt------- AST ADT 大西洋标准时间 BST BDT 白令海标准时间 CST CDT 中部标准时间 EST EDT 东部标准时间 GMT 格林尼治标准时间 HST HDT 阿拉斯加?夏威夷标准时间 MST MDT 山区标准时间 NST 纽芬兰标准时间 PST PDT 太平洋标准时间 YST YDT YUKON标准时间
学习sql有一段时间了,发现在我建了一个用来测试的表(没有建索引)中出现了许多的重复记录。后来总结了一些删除重复记录的方法,在Oracle中,可以通过唯一rowid实现删除重复记录;还可以建临时表来实现...这个只提到其中的几种简单实用的方法,希望可以和大家分享(以表employee为例)。
SQL> desc employee
Name Null? Type ----------------------------------------- -------- ------------------
emp_id NUMBER(10) emp_name VARCHAR2(20)
salary NUMBER(10,2)
可以通过下面的语句查询重复的记录:
SQL> select * from employee;
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
1 sunshine 10000
2 semon 20000
2 semon 20000
3 xyz 30000
2 semon 20000
SQL> select distinct * from employee;
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
3 xyz 30000
SQL> select * from employee group by emp_id,emp_name,salary having count (*)>1
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
SQL> select * from employee e1
where rowid in (select max(rowid) from employe e2 where e1.emp_id=e2.emp_id and
e1.emp_name=e2.emp_name and e1.salary=e2.salary);
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
2. 删除的几种方法:
(1)通过建立临时表来实现
SQL>create table temp_emp as (select distinct * from employee)
SQL> truncate table employee; (清空employee表的数据)
SQL> insert into employee select * from temp_emp; (再将临时表里的内容插回来)
( 2)通过唯一rowid实现删除重复记录.在Oracle中,每一条记录都有一个rowid,rowid在整个数据库中是唯一的,rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。在重复的记录中,可能所有列的内容都相同,但rowid不会相同,所以只要确定出重复记录中那些具有最大或最小rowid的就可以了,其余全部删除。
SQL>delete from employee e2 where rowid not in ( select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--这里用min(rowid)也可以。
SQL>delete from employee e2 where rowid <( select max(e1.rowid) from employee e1 where e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and
e1.salary=e2.salary);
(3)也是通过rowid,但效率更高。
SQL>delete from employee where rowid not in ( select max(t1.rowid) from employee t1 group by
t1.emp_id,t1.emp_name,t1.salary);--这里用min(rowid)也可以。
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
SQL> desc employee
Name Null? Type ----------------------------------------- -------- ------------------
emp_id NUMBER(10) emp_name VARCHAR2(20)
salary NUMBER(10,2)
可以通过下面的语句查询重复的记录:
SQL> select * from employee;
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
1 sunshine 10000
2 semon 20000
2 semon 20000
3 xyz 30000
2 semon 20000
SQL> select distinct * from employee;
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
3 xyz 30000
SQL> select * from employee group by emp_id,emp_name,salary having count (*)>1
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
SQL> select * from employee e1
where rowid in (select max(rowid) from employe e2 where e1.emp_id=e2.emp_id and
e1.emp_name=e2.emp_name and e1.salary=e2.salary);
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
2. 删除的几种方法:
(1)通过建立临时表来实现
SQL>create table temp_emp as (select distinct * from employee)
SQL> truncate table employee; (清空employee表的数据)
SQL> insert into employee select * from temp_emp; (再将临时表里的内容插回来)
( 2)通过唯一rowid实现删除重复记录.在Oracle中,每一条记录都有一个rowid,rowid在整个数据库中是唯一的,rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。在重复的记录中,可能所有列的内容都相同,但rowid不会相同,所以只要确定出重复记录中那些具有最大或最小rowid的就可以了,其余全部删除。
SQL>delete from employee e2 where rowid not in ( select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--这里用min(rowid)也可以。
SQL>delete from employee e2 where rowid <( select max(e1.rowid) from employee e1 where e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and
e1.salary=e2.salary);
(3)也是通过rowid,但效率更高。
SQL>delete from employee where rowid not in ( select max(t1.rowid) from employee t1 group by
t1.emp_id,t1.emp_name,t1.salary);--这里用min(rowid)也可以。
EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
在INFORMIX里执行后出现: Cannot modify table or view used in subquery. :( |
CSDN 网友 ( 2005-10-10) | ||
sql server中你可以加一个自增长的字段 |
rmuyu ( 2005-09-16) | ||
很好,这两天我正在为这个问题烦恼,谢谢楼主 |
sqlsea ( 2005-09-16) | ||
sqlserver里这样: http://blog.itpub.net/post/1626/8887 |
lllllllllluoyi ( 2005-09-15) | ||
我的做法: 一个表abc结构: aa bb cc //字段 -------------------- //值 aa bb cc1 aa bb cc2 aa bb cc3 .................... 从表结构可以看出有CC字段的数据是不同的,这个很重要。 在oracle中: delete from abc where cc in (select cc from abc where aa = 'aa' minus (select cc from abc where aa = 'aa' and rownum <= 1)) and aa = 'aa'; 在sql server中: delete from abc where cc in (select cc from abc where aa = 'aa' and cc not in(select top 1 cc from abc where aa = 'aa')) and aa = 'aa'; 这种情况是删除字段aa相同而其他某个字段不同的方法,如果是每个字段都相同多条记录的删除方法又该是怎么呢? oracle做法: delete from abc t where rowid not in (select max(rowid) from abc t1 where t.aa = t1.aa and t.bb = t1.bb and t.cc = t1.cc) 主要运用了rowid关键字 |