SQL中的DATENAME和DATEPART

Question

I'm trying to get my EntryDate column in this format 'YYYY_m' for example '2013_04'.

This code has been unsuccessful

DATENAME (YYYY, EntryDate) + '_' + DATEPART (M, EntryDate) 

Attempts using DATEFORMAT have also been unsuccessful, stating there was syntax error at ',' after the M. What code would work instead?

Thank you.

Answer 1

select DATENAME (YYYY, EntryDate) 
      + '_' 
      + right('0' + convert(varchar(2),datepart (MM, EntryDate)), 2)

You have to convert the result of DATEPART() to a character string in order for the + to perform an append.

FYI - in the future "unsuccessful" doesn't mean anything. Next time post the actual error you are receiving.

Answer 2

How about date_format() ?

select date_format(EntryDate, '%&Y_%m')

This is the MySQL way. Your code looks like an attempt to do this in SQL Server.

EDIT:

The following should work in SQL Server:

select DATENAME(year, EntryDate) + '_' + RIGHT('00' + DATEPART(month, EntryDate), 2)

Personally, I might use convert() :

select replace(convert(varchar(7), EntryDate, 121), '-', '_')

Answer 3

For example:

SELECT concat(EXTRACT(YEAR FROM '2015/1/1'), '_', 
         LPAD(extract(month from '2014/1/1'),2,'0')) AS OrderYear

This uses

• concat to combine strings
• lpad to place a leading 0 if month is one digit
• and uses extract to pick of the part of date needed.

working fiddle http://sqlfiddle.com/#!2/63b24/8

Answer 4

DATEPART It is a Datetime function which extract information from date. This function always returns result as integer type.

SELECT DATEPART(month, '2009-01-01 00:00:00:000') as month
it is return "1" as an integer:

DATENAME It is also another Datetime function which to extract information from date. This function always returns result as varchar

SELECT DATENAME(month, '2009-01-01 00:00:00:000')  as month
it is return "January".