Questions regarding SQL performance
Posted on 2015-02-12
I have the following questions re sql performance
1- When filtering for a column that is an int, and looking for values 0 or null, what is better for performance to write (columnname = 0 or columnname is null) or isnull(columnname,0)=0.
2- When having two or more conditions in the where clause, does it makes a difference which goes first?
3- Also in the where clause, when having multiple conditions from type where exists (select 1 from tablename where id = ...) and exists (select 1 from tablename where id = ...) and so on, does it makes a difference which table goes first?
4- And on above example is it better to have where exists (select 1 ...) or select null?
5- When checking for a single value is it ok to to write columnnane in ('value') or its better to have columnname = 'value'?