Wrong query: Incorrect syntax near ')' - asp.net

Question

I have ASP.NET application and we use Dapper library. The code that produces the error looks as following:
public bool CheckIfExists(IEnumerable<long> ticketGroups, long dateId, int userId)
{
bool bRetVal = false;
string sql = "if exists (select * from T_TicketGroupsToChangePrice where SubTypeId = #SubTypeId and DateId = #dateId and UserId = #userId)";
using (var conn = CreateSqlConnection())
try
{
int rows = conn.Execute(sql, ticketGroups.Select(g => new { SubTypeId = g, UserId = userId, dateId }));
if (rows > 0)
bRetVal = true;
}
catch (SqlException ex)
{
throw new Exception("Error", ex);
}
return bRetVal;
}
When I run the application it throws the exeption: Incorrect syntax near ')'
As you can see, there can be more tickets (IEnumerable type) with the same date and user.
I'm not sure what's going on.

Answer 1

That is because it is not valid SQL to start with an if (If you mean to use T-SQL it is, but then you have to write the entire if statement)
I think a simple case is what you need:
select case
when exists (select * from T_TicketGroupsToChangePrice where SubTypeId = #SubTypeId and DateId = #dateId and UserId = #userId)
then 1
else 0
end

Answer 2

Your query "if exists (select * from T_TicketGroupsToChangePrice where SubTypeId = #SubTypeId and DateId = #dateId and UserId = #userId)" return some data if the table have some so for that it require something to work on. Like if else condition in programming we can modify this as :
if exists
(select * from T_TicketGroupsToChangePrice where SubTypeId = #SubTypeId and DateId = #dateId and UserId = #userId)
Print 'Have Data'
else
Print 'Don't Have data'
Rewriting your code :
public bool CheckIfExists(IEnumerable<long> ticketGroups, long dateId, int userId)
{
bool bRetVal = false;
string sql = "if exists (select * from T_TicketGroupsToChangePrice where SubTypeId = #SubTypeId and DateId = #dateId and UserId = #userId) Print '**your code to execute if exist data**' else Print '**your code to execute if doesnot exist data**'";
using (var conn = CreateSqlConnection())
try
{
int rows = conn.Execute(sql, ticketGroups.Select(g => new { SubTypeId = g, UserId = userId, DateId = dateId }));
if (rows > 0)
bRetVal = true;
}
catch (SqlException ex)
{
throw new Exception("Error", ex);
}
return bRetVal;
}
this link will help you more :
https://dba.stackexchange.com/questions/30159/exist-select-from-my-table

Answer 3

If your result depends on the number of rows and not on what's returned from the SQL, you could try this:
if exists ([whatever]) select 1
This works, because if there are no matching values, no recordset is returned, and your affected record count is zero.
You could also try something a bit simpler:
select 1
from T_TicketGroupsToChangePrice
where SubTypeId = #SubTypeId
and DateId = #dateId
and UserId = #userId;
But that has the disadvantage of returning one row for however many records you have. This could be a lot, depending on the app and the context, and in any case you don't want to pull over data that you're not going to use.
I wouldn't recommend a CASE statement, because SELECT CASE EXISTS ([whatever]) THEN 1 END will still return one record, and your affected record count will be 1 even if no records exist.
The problem with your original SQL, by the way: The statement is incomplete. You're saying "if exists ..." but you never finish it with the equivalent of a "then". You need to say "if exists() select 1" or something similar.