Ò»¸öSQLÃæÊÔÌâ
ÌâÄ¿ÒªÇó
°¢ÀïbabaµÄÃæÊÔÌâ
ÓÐÈý¸ö±í
ѧÉú±í S
SID SNAME
½Ìʦ¿Î±í T
TID TNAME TCL
³É¼¨±í SC
SID TCL SCR
¸÷×ֶεĺ¬Òå²»ÓÃÎÒ±êÃ÷ÁË°É£¬´óÏÀ¸ç¸çô£¡ºÇºÇ
ÏÖÔÚÒªÇóдSQL²éѯ
1¡¢Ñ¡ÐÞÁËA¡¢B¿Î³Ì£¬²¢ÇÒA¿Î³ÌµÄ³É¼¨´óÓÚB³É¼¨µÄѧÉúÐÕÃû£¿
2¡¢Ã»ÓÐÑ¡ÐÞ‘li’ÀÏʦµÄ¿Î³ÌµÄѧÉú£¬ÒªÇó²»ÄÜÓÃin£¬exists µÈ´Ê£¿
create table SC(
SID varchar(64) ,
TCL varchar(64) ,
SCR int) ;
create table S (
SID varchar(64) ,
SNAME varchar(64)
) ;
create table T
(
TID varchar(64),
TNAME varchar(64),
TCL varchar(64)
) ;
insert into S VALUES ('1','11') ;
insert into S VALUES ('2','22') ;
insert into S VALUES ('3','33') ;
insert into S VALUES ('4','44') ;
insert into SC VALUES ('1','a',100) ;
insert into SC VALUES ('1','b',90) ;
insert into SC VALUES ('2','a',77) ;
insert into SC VALUES ('3','b',34) ;
insert into SC VALUES ('4','a',59) ;
insert into SC VALUES ('4','b',88) ;
insert into T VALUES ('5','li','a');
µÚÒ»¸öÎÊÌâµÄ´ð°¸
select
s.sname,sc1.scr,sc2.scr
from
s,sc sc1,sc sc2
where s.sid=sc1.sid
and s.sid=sc2.sid
and sc1.tcl='a'
and sc2.tcl='b'
and sc1.scr>sc2.scr
ÔËÐнá¹û£º
11 £¬100 £¬ 90
µÚ¶þÌâµÄ´ð°¸
select sid from
(select s.sid,a.tcl from (select sc.sid,sc.tcl from sc,t where sc.tcl=t.tcl and t.tname='li' ) a
right join s
on a.sid=s.sid ) b
where b.tcl is null
ÔËÐнá¹û
3
Ïà¹ØÎĵµ£º
Êýѧº¯Êý
1.¾ø¶ÔÖµ
S:select abs(-1) value
O:select abs(-1) value from dual
2.È¡Õû(´ó)
S:select ceiling(-1.001) value
O:select ceil(-1.001) value from dual
3.È¡Õû£¨Ð¡£©
S:select floor(-1.001) value
O:select floor(-1.001) value from dual
4.È¡Õû£¨½ØÈ¡£©
S:select cast(-1.002 as in ......
Sample1:
/* Variable Declaration */
DECLARE @EmpID AS SMALLINT
DECLARE @SQLQuery AS NVARCHAR(500)
/* Build and Execute a Transact-SQL String with a single parameter value Using EXECUTE Command */
SET @EmpID = 1001
SET @SQLQuery = 'SELECT * from tblEmployees WHERE EmployeeID = ' + CAST(@EmpID A ......
ÏÂÃæµÄÕâЩ½Å±¾¶¼¿ÉÒÔÕÒµ½ÒýÆð´ÅÅÌÅÅÐòµÄSQL¡£
SELECT /*+ rule */ DISTINCT a.SID, a.process, a.serial#,
TO_CHAR (a.logon_time, 'YYYYMMDD HH24:MI:SS') LOGON, a.osuser,TABLESPACE, b.sql_text
from v$session a, v$sql b, v$sort_usage c
WHERE a.sql_address = b.address AND a.saddr = c.session_addr;
......
Èç¹ûÊÇÀàËÆ"select * from user where uid="+uid +" and pwd="+pwd ºÜÈÝÒ׳öÎÊÌâ
ʹÓà SQLParamenter
°ÑÄãµÄSQLÓï¾äд³É ÀàËÆ´æ´¢¹ý³Ì ......
ÔÚSQLServerµÄÐÔÄܵ÷ÓÅÖУ¬ÓÐÒ»¸ö²»¿É±ÈÄâµÄÎÊÌ⣺ÄǾÍÊÇÈçºÎÔÚÒ»¶ÎÐèÒª³¤Ê±¼äµÄ´úÂë»ò±»Æµ·±µ÷ÓõĴúÂëÖд¦ÀíÁÙʱÊý¾Ý¼¯?±í±äÁ¿ºÍÁÙʱ±íÊÇÁ½ÖÖÑ¡Ôñ¡£ÈçºÎÈ·¶¨Ê²Ã´Ê±ºòÓÃÁÙʱ±í£¬Ê²Ã´Ê±ºòÓñí±äÁ¿ÄØ£¿ÁÙʱ±íºÍ±í±äÁ¿¶¼ÓÐÌض¨µÄÊÊÓû·¾³¡£
¡¡¡¡±í±äÁ¿
¡¡¡¡±äÁ¿¶ ......