ifnull <=> nvl Oracle: select nvl(null,1) from dual; Mysql: select ifnull(null,1) from dual; dual is optional in mysql. Oracle needs a ‘from expression’ for all the queries. Dual table is just a dummy to serve that syntax desc dual; Name Null Type ------------------------------ -------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- DUMMY VARCHAR2(1) fetching rownum in oracle and mysql Oracle: select rownum, $column from $table (rownum is a pseudocolumn in oracle) Mysql: select row_number() over() as row_num, $column from $table SET @rownum:=0; SELECT @rownum:=@rownum+1 AS rownum, $column FROM $table (for older mysql versions)