KwickClips Databases and SQL · 38 sec · free
What is a candidate key?
Short answer. Any column that can uniquely identify a row.
How many primary keys can a table have?
One.
Candidate keys
| Column | Unique? |
|---|---|
| AdmNo | Yes |
| Yes | |
| Name | No |
Remember
| Pick one: the primary key |
| Never empty, rarely changes |
Admission number and email are both unique. Which is the primary key? A unique column is a candidate key. Admission number qualifies. Email qualifies too. Name does not. Pick admission number. It is never empty and rarely changes.
This clip is from the full lesson: Keys in a Database: Primary, Candidate, Alternate and Foreign Key — 6 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: CBSE Class 9 Information Technology (402), CBSE Class 10 Information Technology (402), CBSE Class 10 Information Technology (402), CBSE Class 12 Computer Science (083)
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