sql server - SQL : query large table -

i want query large data set in sql - right approach?

declare @datetime datetime  select *  sales  salesdate <= @datetme 

or:

select *  sales  salesdate < (select getdate()) 

or:

select *  sales  salesdate < getdate() 

or using now()

all 3 have same execution plan other 0% assign stage variable in query no. 1. turn out practice in long run initialize variable datetime , use comparison. when have long comparisons make way, user habit of formatting datetime in variable , comparing column against variables. otherwise, becomes habit of formatting sql column , comapring date. formats datetime field in every data row comparison value , makes datetime comparisons slow.

for particular query, readability , ease of use, can select query no. 3 [select * sales salesdate < getdate()].

wiki