There is some difficulty when trying to create a join between two tables when the desired field to join with is the last column in the table view window. Sometimes Toad will use the next column in the table instead of the selected column.
In this example I want to join INVENTORY to DESC_INV_MERCH_CODE_1 on INVENTORY.FLAG_MERCH_CODE_1 = DESC_INV_MERCH_CODE_1.MERCH_CODE_1, as this will allow me to bring in the description of the code.
I put the pointer on INVENTORY.FLAG_MERCH_CODE_1, click-and-drag, drop onto DESC_INV_MERCH_CODE_1.MERCH_CODE_1. Eventhough Toad puts the focus onto FLAG_MERCH_CODE_1, Toad makes the join using the next column below INVENTORY.FLAG_MERCH_CODE_1; INVENTORY.FLAG_HIDE_FROM_WEB.