error in table search when I use bd join data

franzzco

I'm using data tables with a code-maker, but I have a problem looking in the table for one of the fields, the database field saves a numerical value, but I show in the table the value in the name that you want to join with another table to tell me the name of that identification, the problem is that when looking in the error table all the time if I use the join.
example.
field of my table products category_id = 1
in the table categories category id = 1 name = first.

In the table the first name appears in the category column, when I use join between the products and categories table, but I get an error when I try to search the table, but if I do not use join, I do not get an error but the results in the column the table shows the numerical value and not the name, that is, category = 1.