Where Clause from Another table - sql

Question

So the goal is to make a SQL query for table A but the where clause is stored in table B.
here is example
table B:
BatchNumber | DataItem | Operator | TValue
12345 | Branch | = | 2700
12345 | StockType| = |S
12345 | PRCode | <> |AD
from this table I need to make below where statement
select *
from testdata.TableA
where Branch = 2700 and StockType = 'S' and PRCode <> 'AD'
here are the different methods I tried using to form a sql
declare #whereClause varchar(400)
declare #schema varchar(10) = 'testdata'
declare #Batch varchar(15) = 12345
select #whereClause = N' COALESCE(#whereClause + ' ' ,'') + trim(DataItem) + ' ' + trim(Operator) + ' ' +
case
when trim(TValue) LIKE '[A-Za-z]%' then '''' + trim(TValue) + '''' + ' AND'
when trim(TValue) = ' ' then '''' + '''' + ' AND'
else trim(TValue) + ' AND'
end
from' + #schema + '.TableB where BatchNumber =' + #Batch
--remove AND from the end of statement
SET #whereClause = SUBSTRING(#whereClause,0, LEN(#whereClause) - 3)
PRINT #whereClause
However this is giving me syntax error with single codes in the case statement.
Msg 102, Level 15, State 1, Line 4
Incorrect syntax near ' ,') + trim(DataItem) + '.
I need case statement to add single quote around string operators.
I also tried different method with FOR XML PATH(''), but with this single quotes are eliminated and "<>" signs are changed to "gtlt"
really appreciate any help.

Answer 1

It seems like some of your single-quotations may have to be quoted or you could use variables. For example: #whereClause = N' COALESCE(#whereClause + ' ' ,'')... may require #whereClause = N' COALESCE(#whereClause + '' '' ,'''')... or something on those lines. You could store there result of COALESCE(#whereClause + ' ' ,'') in a variable and then concat it with other variables in a similar way.
Alternatively, you could write a query in SQL Server like this:
select 'select * '
union all select 'from testdata.TableA '
union all select 'where 1 = 1 '
union all
select concat(
' and ',
dataitem, ' ', operator, ' ',
case
when tvalue like '%[0-9]%' then tvalue
else concat('''', tvalue, '''')
end
)
from test /* or tableB */
where batchnumber = 12345; /*optional where clause*/
You'll get the output like this:
select *
from testdata.TableA
where 1 = 1
and Branch = 2700
and StockType = 'S'
and PRCode <> 'AD'
Example:
https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=12c3110a0d82e754bfc16f686779cddd