SELECT TOP 1
Means Selecting the very 1st record in the result set
SELECT 1
Means return 1 as the result set
SELECT TOP 1 1 FROM [SomeTable] WHERE <SomeCondition>
Means if the condition is true and any rows are returned from the select, only return top 1
row and only return integer 1
for the row (no data just the integer 1 is returned).