A simple join between topic items, shown in Figure 5, Simple Join Between Identical Store Key Fields in Two Topics, retrieves rows where the values in joined columns match.
Joins need to occur between items containing the same data. Often, the item names between two topics are identical, which sometimes indicates which items join. When selecting items to join, recognize that two items may share the same name, but refer to completely different data. For example, an item called “Name” in a Customer table and an item called “Name” in a Product table are probably unrelated.