If A is a foreign key in R, no null values are permitted in the column A in any instance of R. True False

Analysis of the Statement

1. Understanding Foreign Keys: A foreign key is a field (or collection of fields) in one table that uniquely identifies a row in another table. The foreign key creates a relationship between the two tables.

2. Null Values in Foreign Key Columns: Generally, the use of foreign keys allows for the column to contain null values under certain circumstances. This typically happens when the relationship between the tables is optional.

3. Constraints on Foreign Keys: While it's true that foreign keys establish a link between two tables, it is not inherently true that they cannot contain nulls. If the foreign key is defined as NOT NULL, then nulls will not be permitted. However, if no such constraint is set, null values can be present to indicate that there is no related entry in the linked table.

Conclusion

Based on the above analysis, the statement "If A is a foreign key in R, no null values are permitted in the column A in any instance of R" is False. While certain implementations can restrict nulls, it is not a universal rule for all foreign keys.