PostgreSQL date calculation functions, postgresql Functions

PostgreSQL date calculation functions, postgresql Functions

I. connector in each data

SqlServer connector: + (plus sign)

Sqlite connector:. (point)

PostgreSQL connector: | (OR)

II:

Today, when I was computing data in PostgreSQL, I had to record a few materials ~!

Functions and variables used

To_char (), Date (), now (), current_date

Calculate the difference between two dates

Current_date is the date of today, which is

Date ('1970-06-05 ')-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

III:

select now() + interval '1 days'; 

select now() + interval '1 month'; 

select now() + interval '1 years'; 

IV:

SQL Server uses functions for date calculation.

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