Question

Topic: Database Design

What are some concerns about using a date (or date time) as a primary key?

Answer 1

• First, let's assume that we are using the georgian calendar. As you may know, this calender waas adopted to replace the jukian calendar in most western countries, but they did not all do it on the same day. The change has taken hundred of yearsbetween 1582 and the twentieth century, and during that time, what was May 13th for one person was May 24th for someone else.
• So the second assumption is that we are going to store dates in our databases only from the current era. This is because dateis any of those earlier years is not enough to pin down exactly what day it was, more information would be needed, whether it is georgian or julian calendar date.
• You see that is the purpose of primary key: to give identify to a real world entity. what we are identifying when we use a date is a particular day.
• Primary key should be

1. it is never null
2.it uniquely identifies each row in the table

• So on the basis of this date makes an excellent primary key. But it is never easy to keep date as a primary key because when we use this primary key as a foreign key in another table then it is difficult to handle. Also the there cannot be auto-increment in the date so we have to keep it unique manually which is difficult. so these are some concerns of date as a primary key.