MySQL IF(EXPRESSION, A, B) equivalent in PL/SQL (Oracle)

In MySQL, we can 

SELECT IF(A IS NULL, "something", A) FROM some_table;

If you want to do a similar thing in PL/SQL, you need to

SELECT (CASE WHEN A IS NULL THEN "something" ELSE A END) FROM some_table;

If you want to get the first non-null value from several fields, you have a better choice than using the CASE keyword.

SELECT COALESCE(A, B) FROM some_table

see more information about the Oracle COALESCE function