I need to search on two fields using LIKE function and should match also in reverse order. My table uses InnoDB which dont have Full text search.
Consider the following
You need to re-state the concat expression in your where clause.
SELECT CONCAT(first_name, ' ', last_name) as fullname FROM users WHERE CONCAT(first_name, ' ', last_name) LIKE '%doe%';
Unfortunately "as" just create a column alias, not a variable that you can use elsewhere.