一:各个数据中的连接符
SqlServer的连接符:+(加号)
Sqlite的连接符:.(点)
PostgreSQL的连接符:||(或)
二:
今天在PostgreSQL计算日期的时候,翻了一些资料,很少,就记录下来吧~!
其中使用到的函数及变量
to_char()、Date()、now()、current_date
计算两个日期的差
current_date为今天的日期,为:2015-06-03
Date('2015-06-05')-current_date=2
select to_char(current_date,'yyyy')||'-'||to_char(birthday,'mm-dd'),Date(to_char(current_date,'yyyy')||'-'||to_char(birthday,'mm-dd'))-current_date
from tablename where delflag=0 and status=0
and Date(to_char(current_date,'yyyy')||'-'||to_char(birthday,'mm-dd'))-current_date>=0
and Date(to_char(current_date,'yyyy')||'-'||to_char(birthday,'mm-dd'))-current_date<=7 order by birthday desc
三:
select now() + interval '1 days';
select now() + interval '1 month';
select now() + interval '1 years';
四:
SqlServer中进行日期计算时,用到函数
CONVERT(),DATEPART(),getDate()
select CONVERT(varchar(10),CONVERT(varchar(4),DATEPART(year,getDate()))+'-'+ CONVERT(varchar(2),DATEPART(month,birthday))+'-'+CONVERT(varchar(2),DATEPART(day,birthday)),120),datediff(day,CONVERT(varchar(10),getdate(),120),CONVERT(varchar(10),CONVERT(varchar(4),DATEPART(year,getDate()))+'-'+ CONVERT(varchar(2),DATEPART(month,birthday))+'-'+CONVERT(varchar(2),DATEPART(day,birthday)),120))
from tablename where delflag=0 and status=0
and datediff(day,CONVERT(varchar(10),getdate(),120),CONVERT(varchar(10),CONVERT(varchar(4),DATEPART(year,getDate()))+'-'+ CONVERT(varchar(2),DATEPART(month,birthday))+'-'+CONVERT(varchar(2),DATEPART(day,birthday)),120))<=7
and datediff(day,CONVERT(varchar(10),getdate(),120),CONVERT(varchar(10),CONVERT(varchar(4),DATEPART(year,getDate()))+'-'+ CONVERT(varchar(2),DATEPART(month,birthday))+'-'+CONVERT(varchar(2),DATEPART(day,birthday)),120))>=0 order by birthday desc