How to replace EQUAL TO by LIKE in a Query involving variables

Question

Dear All,
I am working on a Query which is in reality 3 Queries in 1. It works perfectly.
When I run the Query, it gives the following Query - Selection Criteria
Query - Selection Criteria
Import Log                        ...................
Block Number                      ...................
Document Date                     ...................
Document Date                     ...................
[OK]   [Cancel]
To use this Query, we must choose only 1 criterion and leave other fields blank. To achieve this, I
use OR inside WHERE
1ST Query
If you type S713 in the first field, it returns all records with Import Log = S713
2 ND Query
If you type G1575 in the 2ND field, it returns all records with Block Number = G1575
3rd  Query
If you type '01.07.11' and '05.07.11' in the 3RD and 4TH fieldS, it returns all records with
Dates between 01.07.00 and 05.07.11
The Query won't work if you fill in all fields.
WHAT I WANT?
I want to replace the EQUAL TO in the WHERE clause by LIKE to allow the Query to search for a pattern, instead
of rendering an exact match.
I know this can be done with  = '[%1]' by changing it to LIKE '%[%1]%'
But how can you do the same with @shipnum and @reqnum?
I can change the variable declarations to
set @shipnum = /*   */ '%[%1]%'
but it creates problems.
How can we use LIKE in the WHERE clause, without modifying the declarations.
Thanks
Leon Lai
Here's my Query
TABLES:
T0 = OPCH A/P Invoice - Header
T1 = PCH1 A/P Invoice - Rows
T5 = OJDT Journal Entry
declare @shipnum nvarchar (30)
set @shipnum =
/*select T1.[ImportLog] from [dbo].[PCH1] T1 where T1.[ImportLog]*/ '[%1]'
declare @reqnum nvarchar (30)
set @reqnum =
/*select T1.[BlockNum] from [dbo].[PCH1] T1 where T1.[BlockNum]*/ '[%2]'
declare @taxdt1 datetime
set @taxdt1=
/*select T0.[TaxDate] from [dbo].[OPCH] T0 where T0.[TaxDate]*/ '[%3]'
declare @taxdt2 datetime
set @taxdt2=
/*select T0.[TaxDate] from [dbo].[OPCH] T0 where T0.[TaxDate]*/ '[%4]'
SELECT
T0.[TaxDate] AS 'Doc Dt',
T1.[ImportLog] AS 'Ship #',
T1.[BlockNum] AS 'Reqn #',
T0.[CardName] AS 'Supplier Name',
T0.[DocTotal] AS 'Rs'
FROM [dbo].[OPCH] T0
INNER JOIN [dbo].[PCH1] T1 ON T0.[DocEntry] = T1.[DocEntry]
INNER JOIN [dbo].[OJDT] T5 ON T0.[TransID] = T5.[TransID]
WHERE
(T1.[ImportLog]  = @shipnum  AND
@reqnum = '  ' AND
@taxdt1  = '  ' AND
@taxdt2  = '  ' )
OR
(T1.[BlockNum] = @reqnum  AND
@shipnum = '  ' AND
@taxdt1  = '  ' AND
@taxdt2  = '  ' )
OR
(T0.[TaxDate] >= @taxdt1 AND
T0.[TaxDate] <= @taxdt2 AND
@shipnum = ' ' AND
@reqnum = ' ' )

Answer 1

Dear Gordon,
Thanks for your reply.
Unfortunately it does not work when I use
T1.[ImportLog]  LIKE '%@shipnum%'
I think I could guess the reason:
Since @shipnum means '% { %1 } %'             
/* I use { } to represent Square Brackets */
Then
LIKE '%@shipnum%'  would mean
LIKE '% '%{%1}%'    '
and this would be incorrect syntax.
If I remove the ' it still does not work.
By numerous trial and error, I just arrived at  this mixture of @variable and '{%x}' which works!
I have no idea why, and it appears rather messy.But it works seamlessly.
I tried using uniquely {%x} without the @variables. It does not work.
So, if you could analyse it and put it in neater form (I mean without a mixture of @ and { },
I would be grateful.
There are so many tricks I used to make my Queries work, without understanding
at all why they work.
Best Regards,
Leon Lai
TABLES:
T0 = OPCH A/P Invoice - Header
T1 = PCH1 A/P Invoice - Rows
T5 = OJDT Journal Entry
declare @shipnum nvarchar (30)
set @shipnum =
/*select T1.[ImportLog] from [dbo].[PCH1] T1 where T1.[ImportLog]*/ '%[%1]%'
declare @reqnum nvarchar (30)
set @reqnum =
/*select T1.[BlockNum] from [dbo].[PCH1] T1 where T1.[BlockNum]*/ '%[%2]%'
declare @taxdt1 datetime
set @taxdt1=
/*select T0.[TaxDate] from [dbo].[OPCH] T0 where T0.[TaxDate]*/ '[%3]'
declare @taxdt2 datetime
set @taxdt2=
/*select T0.[TaxDate] from [dbo].[OPCH] T0 where T0.[TaxDate]*/ '[%4]'
SELECT
T0.[TaxDate] AS 'Doc Dt',
T1.[ImportLog] AS 'Ship #',
T1.[BlockNum] AS 'Reqn #',
T0.[CardName] AS 'Supplier Name',
T0.[DocTotal] AS 'Rs'
FROM [dbo].[OPCH] T0
INNER JOIN [dbo].[PCH1] T1 ON T0.[DocEntry] = T1.[DocEntry]
INNER JOIN [dbo].[OJDT] T5 ON T0.[TransID] = T5.[TransID]
WHERE
(T1.[ImportLog]  like @shipnum  AND
'[%2]'  = '  '  AND
@taxdt1  = '  ' AND
@taxdt2  = '  ' )
OR
(T1.[BlockNum] like @reqnum  AND
'[%1]' = '  ' AND
@taxdt1  = '  ' AND
@taxdt2  = '  ' )
OR
(T0.[TaxDate] >= @taxdt1 AND
T0.[TaxDate] <= @taxdt2 AND
'[%1]' = ' ' AND
'[%2]'= ' ' )