How to join tables without identifiers? For school I have to do this:

Query what salary scale an employee belongs to displaying these columns: 

s_schaal.schaal, werknemer.name, werknemer.salaris


But there are no identifiers between the tables. All I have is a bottom line and upper line column (s_schaal.ondergens &amp; s_schaal.bovengrens). 

What MySQL query can I use to compare and join this data?
I finally figured that joining these tables would not bring a solution. I solved it doing this:

SELECT S.schaal, W.wnr, W.wnaam, W.salaris FROM Werknemer W, S_schaal S 
WHERE W.salaris &gt;= S.ondergrens &amp;&amp; W.salaris &lt;= S.bovengrens;