SQL problem with multi field searches

I am having some problems here, I have actually had the same issue for a while now but I hack around and get it working in the end however I would like to know if I have missed a simple way of开发者_StackOverflow doing it.

Say if I have:

Field input 1 
Field input 2
Field input 3 (empty)
Field input 4

I want to query SELECT * FROM tbl_table WHERE field1 LIKE ? AND field2 LIKE  ? AND field3 LIKE  ? AND field4 LIKE  ? 

Basically I come into trouble when an input is empty because its searching in a field and looking for null or another string when I want it to just discard the LIKE operator of the empty Input.

I know this might read really bad however its hard to get a point across some times.

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SELECT * FROM tbl_table WHERE (field1 IS NULL OR field1 LIKE ?) AND (field2 IS NULL OR field2 LIKE ?) AND ....

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Essentially, you need to check the value of the variable in the where clause. Check if it is null or has value like this.

Declare @input1 varchar(50);
Declare @input2 varchar(50);
Declare @input3 varchar(50); 
Declare @input4 varchar(50);

SET @input1 = 'a'
SET @input2 = 'b'
SET @input3 = NULL
SET @input4 = 'c'

SELECT 
  * 
FROM tbl_table 
WHERE 
  (@input1 is null OR field1 LIKE @input1) 
  AND (@input2 is null OR field1 LIKE @input2) 
  AND (@input3 is null OR field1 LIKE @input3) 
  AND (@input4 is null OR field1 LIKE @input4)