What does Select 1 means

Question

Hi

What does Select 1 means in below code

Case
    When EXISTS (Select 1 from INV4 where "DocEntry" = T0."DocEntry" and "StcCode" = t2."StcCode" and "staType" = '-120')
    then sum(t2."BaseSum") else sum(t2."BaseSum")/2 End As "BaseSum"

Thanks

Daniel Wright · Answer

Absolutely! In SQL, the query "Select 1" is commonly used within an EXISTS clause to check for the existence of at least one row that meets specific conditions, without actually retrieving any data. Here's a breakdown of the code snippet you provided: - The SELECT 1 statement inside the EXISTS function is a way to optimize the query because it merely checks for the presence of a row rather than retrieving actual row data, which can improve performance. - In your specific SQL query, the EXISTS (Select 1 from INV4...) part is checking whether there is at least one row in the table INV4 that satisfies the conditions specified in the WHERE clause. - If there is at least one row that meets the criteria ("DocEntry" = T0."DocEntry" and "StcCode" = t2."StcCode" and "staType" = '-120'), then the CASE statement will return the sum of t2."BaseSum". Otherwise, it will return half of the sum of t2."BaseSum". So, in summary, the "SELECT 1" statement is a smart way to perform a check for existence without the need to fetch actual data, thus enhancing the query's efficiency. If you have any more questions or need further clarification, feel free to ask!