How to solve the date comparison issue in SQL Server? - sql-server

Question

I am using the following way to compare two dates:
if CONVERT(varchar(20), #ScheduleDate, 101) >= CONVERT(varchar(20), #CurrentDateTime, 101)
This is working fine for the current year, but when the comes in yearly like one date is 12/31/2012 and 1/1/2013 then its not working.
Please help me how can I resolve this.

Answer 1

why do you comparing strings?
you can compare dates
if #ScheduleDate >= #CurrentDateTime
but if your date contains time, I usually do
if convert(nvarchar(8), #ScheduleDate, 112) >= convert(nvarchar(8), #CurrentDateTime, 112)
112 datetime format is YYYYMMDD so it's good for compare dates

Answer 2

You have to remember that string comparison is from left to right, so "1/...." is smaller than "12/...".
You need to use DATETIME comparisons, not string comparison.
Something like
DECLARE #ScheduleDate DATETIME = '1/1/2013',
#CurrentDateTime DATETIME = '12/31/2012'
IF (#ScheduleDate >= #CurrentDateTime)
BEGIN
SELECT #ScheduleDate, #CurrentDateTime
END
DECLARE #ScheduleDateString VARCHAR(20) = '1/1/2013',
#CurrentDateTimeString VARCHAR(20) = '12/31/2012'
IF (CONVERT(DATETIME,#ScheduleDateString,101)>=CONVERT(DATETIME,#CurrentDateTimeString,101))
BEGIN
SELECT CONVERT(DATETIME,#ScheduleDateString,101),CONVERT(DATETIME,#CurrentDateTimeString,101)
END
SQL Fiddle DEMO
Note that if the variables are already datetimes, you do not need to convert them.

Answer 3

Assuming that both variables are currently DateTime variables, can't you just compare them without converting to strings?
declare #ScheduleDate DATETIME, #CurrentDateTime DATETIME
SET #ScheduleDate = '1 Jan 2013'
SET #CurrentDateTime = GetDate()
IF (#ScheduleDate >= #CurrentDateTime)
BEGIN
SELECT 'Do Something'
END
ELSE
BEGIN
SELECT 'Do Something Else'
END

Answer 4

when you use CONVERT(nvarchar(8), #ScheduleDate, 112) function it's return string instead of date.
so,
Use "112" DateFormat in Sql Server it's return string in "YMD" format without any sepration.
compare that string in your query and get desire output.
Such as "if CONVERT(nvarchar(8), #ScheduleDate, 112) >= CONVERT(nvarchar(8), #CurrentDateTime, 112)"

Answer 5

I would not use CONVERT to compare formatted strings. It is slow (well, more like microseconds, but still)
I use a UDF for SQL prior to version 2008
CREATE FUNCTION [dbo].[DateOnly] (#Date DateTime)
RETURNS Datetime AS
BEGIN
Return cast (floor (cast (#Date as float)) as DateTime)
END
and for versions >=2008 this approach
select convert(#MyDateTime as DATE)
Of course, you can compare datetime values directly, but to know whether two datetime values are on the same date (ignoring the time component), the above versions have proven to be effectivy.

Answer 6

Date : From and To with following format
from_Date# = #dateformat("#form.from#", "mm/dd/yyyy")
to_Date# = #dateformat("#now()#" + 1, "mm/dd/yyyy")
In SQL Statement
WHERE a.DateCreated >= CAST ('#from_date#' AS DATE) and a.DateCreated <= CAST('#to_date#' AS DATE)
This is working fine without any cast of original date time column