sql—datediff º¯Êý
DATEDIFF
·µ»Ø¿çÁ½¸öÖ¸¶¨ÈÕÆÚµÄÈÕÆÚºÍʱ¼ä±ß½çÊý¡£
Ò»¡¢ Óï·¨
DATEDIFF ( datepart , startdate , enddate )
¶þ¡¢²ÎÊý
datepart
Êǹ涨ÁËÓ¦ÔÚÈÕÆÚµÄÄÄÒ»²¿·Ö¼ÆËã²î¶îµÄ²ÎÊý¡£Ï±íÁгöÁË Microsoft® SQL Server™ ʶ±ðµÄÈÕÆÚ²¿·ÖºÍËõд¡£
ÈÕÆÚ²¿·Ö Ëõд
year yy, yyyy
quarter qq, q
Month mm, m
dayofyear dy, y
Day dd, d
Week wk, ww
Hour hh
minute mi, n
second ss, s
millisecond ms
startdate
ÊǼÆËãµÄ¿ªÊ¼ÈÕÆÚ¡£startdate ÊÇ·µ»Ø datetime »ò smalldatetime Öµ»òÈÕÆÚ¸ñʽ×Ö·û´®µÄ±í´ïʽ¡£
ÒòΪ smalldatetime Ö»¾«È·µ½·ÖÖÓ£¬ËùÒÔµ±Óà smalldatetime ֵʱ£¬ÃëºÍºÁÃë×ÜÊÇ 0¡£
Èç¹ûÄúÖ»Ö¸¶¨Äê·ÝµÄ×îºóÁ½Î»Êý×Ö£¬ÔòСÓÚ»òµÈÓÚ"Á½Î»ÊýÄê·Ý½ØÖ¹ÆÚ"ÅäÖÃÑ¡ÏîµÄÖµµÄ×îºóÁ½Î»Êý×ÖµÄÊý×ÖËùÔÚÊÀ¼ÍÓë½ØÖ¹ÄêËùÔÚÊÀ¼ÍÏàͬ¡£´óÓÚ¸ÃÑ¡ÏîµÄÖµµÄ×îºóÁ½Î»Êý×ÖµÄÊý×ÖËùÔÚÊÀ¼ÍΪ½ØÖ¹ÄêËùÔÚÊÀ¼ÍµÄÇ°Ò»¸öÊÀ¼Í¡£ÀýÈ磬Èç¹û two digit year cutoff Ϊ 2049£¨Ä¬ÈÏ£©£¬Ôò 49 ±»½âÊÍΪ 2049£¬2050 ±»½âÊÍΪ 1950¡£Îª±ÜÃâÄ£ºý£¬ÇëʹÓÃËÄλÊýµÄÄê·Ý¡£
enddate
ÊǼÆËãµÄÖÕÖ¹ÈÕÆÚ¡£enddate ÊÇ·µ»Ø datetime »ò smalldatetime Öµ»òÈÕÆÚ¸ñʽ×Ö·û´®µÄ±í´ïʽ¡£
Èý¡¢·µ»ØÀàÐÍ
integer
ËÄ¡¢Ó÷¨
´Ëº¯Êý¼ÆËãÁ½¸öÖ¸¶¨ÈÕÆÚÖ®¼äÈÕÆÚ²¿·ÖµÄÊýÄ¿¡£½á¹ûΪÈÕÆÚ²¿·Ö
Ïà¹ØÎĵµ£º
Microsoft SQL Server2005¼¼ÊõÄÚÄ»:T-SQL³ÌÐòÉè¼Æ
http://www.amazon.cn/mn/detailApp/ref=sr_1_25?_encoding=UTF8&s=books&qid=1261538877&asin=B0011C2568&sr=8-25
Microsoft SQL Server 2005¼¼ÊõÄÚÄ»£º²éѯ¡¢µ÷ÕûºÍÓÅ»¯
http://www.amazon.cn/mn/detailApp/ref=sr_1_4?_encoding=UTF8&s=books&am ......
--ÈÕÆÚת»»²ÎÊý,ÖµµÃÊÕ²Ø
select CONVERT(varchar, getdate(), 120 )2004-09-12 11:06:08
select replace(replace(replace(CONVERT(varchar, getdate(), 120 ),'-',''),' ',''),':','')20040912110608
select CONVERT(varchar(12) , getdate(), 111 )2004/09/12
select CONVERT(varchar(12) , getdate(), 112 )20040912 ......
use myoa
select * from
delete from department where departmentid=1
insert Department(DepartmentId,DepartmentName) values(1,'¼¼Êõ²¿')
update Department set departmentname='ÐÅÏ¢¼¼Êõ²¿' where departmentid=1
--ɾ³ý±í
drop table department
--ɾ³ýÊý¾Ý¿â
drop database bai
--ͳ¼ÆÊý¾Ý¿â±íÖмǼ
se ......
1. GROUP BY ÊÇ·Ö×é²éѯ, Ò»°ã GROUP BY ÊǺ;ۺϺ¯ÊýÅäºÏʹÓÃ
group by ÓÐÒ»¸öÔÔò,¾ÍÊÇ select ºóÃæµÄËùÓÐÁÐÖÐ,ûÓÐʹÓþۺϺ¯ÊýµÄÁÐ,±ØÐë³öÏÖÔÚ group by ºóÃ棨ÖØÒª£©
ÀýÈç,ÓÐÈçÏÂÊý¾Ý¿â±í£º
A B
1 abc
1 bcd
1 asdfg
Èç¹ûÓÐÈ ......
ÔÚLINQ to EntitiesÖÐûÓа취ÔÙÏñ LINQ to SQL ÖÐÒ»ÑùʹÓà Contains µÄ·½·¨À´ÊµÏÖsql "in" ¹Ø¼ü×Ö
ÏÂÃæ´úÂëÔÚ LINQ to SQL ÖпÉÐÐ ÔÚLINQ to EntitiesÈ´ÎÞ·¨ÔËÐУº
var s = db.Account.Select(c => c.ID);
var ret =(from t in db.Profile
where&n ......