How do I perform an IF…THEN in an SQL SELECT?

Question

How do I perform an IF...THEN in an SQL SELECT statement?

For example:

SELECT IF(Obsolete = \'N\' OR InStock = \'Y\' ? 1 :          


        

Answer 1

If you're inserting results into a table for the first time, rather than transferring results from one table to another, this works in Oracle 11.2g:

INSERT INTO customers (last_name, first_name, city)
    SELECT 'Doe', 'John', 'Chicago' FROM dual
    WHERE NOT EXISTS 
        (SELECT '1' from customers 
            where last_name = 'Doe' 
            and first_name = 'John'
            and city = 'Chicago');