Final answer:
For a query joining five tables, it is necessary to have four join conditions to properly link the tables together without creating a Cartesian product.
Step-by-step explanation:
When joining multiple tables in a database, the general rule is that you need N-1 join conditions for N tables. So, for a query joining five tables, you would require four join conditions. This ensures each table is joined based on a common field to the next, forming a chain of joins that connect all the tables together. This is crucial for accurate data retrieval and to avoid Cartesian products, where tables are combined with all possible combinations which often lead to incorrect results.