SEARCH ARGUMENTS v7.0
When writing SQL queries, it is important to realize what constitutes a 
good search argument. Knowing the difference can mean either a well-
performing query or a poorly performing query. The placement of 
arguments within the WHERE clause can influence the efficiency of a 
query.

Search arguments are usually variables of a known quantity and are 
specified in the WHERE clause of a SQL query.

SELECT * FROM TableX WHERE Amount = 876

or 
DECLARE @Amt int 
SET @Amt = 1234 

SELECT * FROM TableX WHERE Amount = @Amt

The constant value 1234 and the @Amt variable are valid search 
arguments. These values are known at runtime when SQL Server executes 
the query.

SELECT * FROM TableX WHERE Amount * 2 = 876 
or 
DECLARE @Amt int 
SET @Amt = 1234 

SELECT * FROM TableX WHERE Amount * 2 = @Amt

The constant value 876 and the @Amt variable are good search arguments 
but notice the Amount * 2 on the left side of the equal sign. This is a 
valid query but, since the SQL optimizer does not know the value at 
runtime, SQL Server may need to scan the table in order to fulfill this 
query. As we know, table scans, by most accounts, are considered 
inefficient.

The idea is to keep good search arguments on the right side of the 
operator (=, <, >=, etc) and avoid using calculations and functions on 
the left side of the operator. Using this method should have results 
returned faster to the user.

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