Oracle to Mysql Migration
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)
sqlines is a good resource on this topic.