How do i check if something exist in a SQL db?

Question

Right now using SQLite i write the below (I may move to either mysql or ms sql)

command.CommandText = "SELECT count(reset_key) user_data WHERE reset_key=@key;";

This works but is there a more optimized or cleaner way?

Answer 1

That's about the cleanest, most optimized way there is. Make sure that there's an index on reset_key and it will be very, very fast.

Answer 2

Try

  Select Case When Exists (Select * From user_Data
                           Where reset_key = @key)
              Then 1 Else 0 End

Answer 3

SQLite has the support of LIMIT clause. That might help.

EDIT: I don't know the SQLite syntax. But in SQL sense, it would look like

Select 1 From user_Data Where reset_key = @key LIMIT 1

Answer 4

command.CommandText = "SELECT TOP 1 1 FROM user_data WHERE reset_key=@key"

if (commmand.ExecuteScalar() == null)
{
    //code for no matches here
}