whether value is repeated in database? - sql

Question

IF EXISTS ( 'SELECT ' +#TextField+','+#ValueField+' FROM ' + #TableName + ' WHERE ' + #TextFieldPara + '=' +#ValueFieldPara + ' ORDER BY ' +#TextField+' ASC;')
BEGIN
SET #Message = #TextField + ' Already Exist...'
END
ELSE
BEGIN
SET #Message = 'TRUE'
END
by using this query i am trying to check in all table whether inserted value for field Repeated or Not.
when i write this query in store procedure i got an error at
IF EXISTS ( 'SELECT ' +#TextField+','+#ValueField+' FROM ' + #TableName + ' WHERE ' + #TextFieldPara + '=' +#ValueFieldPara + ' ORDER BY ' +#TextField+' ASC;') "
all variables are populated from c# back end.
is there any solution?

Answer 1

If you want to set the table, you need dynamic SQL. Here is one method:
declare #sql nvarchar(max);
declare #cnt int;
set #sql = '
SELECT #cnt = COUNT(*)
FROM #TableName
WHERE #TextFieldPara = #ValueFieldPara
');
set #sql = replace(#sql, '#TableName', #TableName);
set #sql = replace(#sql, '#TextFieldPara', #TextFieldPara);
set #sql = replace(#sql, '#ValueFieldPara', #ValueFieldPara);
exec sp_executesql(#sql, N'#cnt int output', #cnt=#cnt output);
if (#cnt > 0) . . .
begin
set #Message = #TextField + ' Already Exist...';
end
else
begin
set #Message = 'TRUE';
end;
I simplified the query because you don't need a select list or order by for determining the existing of values. I also used count(*) just because it is simpler to express. If you care about performance, there are better methods, such as a case with an exists in it.
Similarly, you should use quotename() for the identifiers in the query. You don't have that in your sample code, but it is a best practice.