ECDL Exam ECDL-ADVANCED Topic 2 Question 7 Discussion

A table usually has a column or combination of columns whose values uniquely identify each row in the table. This column (or columns) is called the primary key. Primary key ensures that no duplicate or null values are entered in the column (or columns) defined as primary key columns. This enforces integrity of the table. A primary key can be created by defining a primary key constraint while creating or altering a table. A table can have only one primary key constraint. As primary key constraints ensure uniqueness, they are often defined by using an identity column.

Answer option D is incorrect. It is not important to consider the size of a primary key.

Answer option C is incorrect. For using a database, it is not necessary to remember record keys.

Answer option A is incorrect. A simple datatype is helpful in the key indexing, but it is not a primary characteristic.

Chapter: DATABASE, ADVANCED-LEVEL

Objective: Table Design