Hello there. Real noob here with kotlin and exposed. I'm trying to run a simple join but clearly I'm missing something obvious so I was trying to recreate what I read on the wiki. AccessToken.idStaff and Staff.id are both int. The exception says that "Cannot join as there is no matching primary key/ foreign key pair and constraint missing". Isn't that "select" the condition for the join?

(AccessToken innerJoin Staff).slice(Staff.id, Staff.userName).select {AccessToken.idStaff eq Staff.id}

If

AccessToken

table has reference to

Staff

table, than your first code will also work. Look here https://github.com/JetBrains/Exposed/wiki/DAO#simple-reference