Final answer:
A key field in the same format is not necessary for a successful table join. Unique values and the ability to establish a relationship between the tables are more important.
Step-by-step explanation:
When joining tables, a key field in the same format is not necessary for a successful table join. The key field is used to match records from the two tables, so as long as the key values have the same meaning and can be used to establish the relationship between the tables, they do not need to be in the same format. However, it is important that the key field has the same unique values in both tables, as this ensures a proper match.
For example, if you have a table of students with an ID field as the key, and another table of courses with a Student ID field as the key, the format of the ID field (e.g., integer or string) does not matter as long as the values are unique and can be used to establish the relationship between the tables.
Therefore, the correct answer is a) Key field in the same format.