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KwickClips Databases and SQL · 39 sec · free

Why can a name not be a key?

Short answer. Because names can repeat.

Can a key value be empty?

No.

Add a unique column

AdmNoName
1001Riya Shah
1003Riya Shah

Remember

Every row needs a unique value
That column is a key

Two students share one name. Which one paid the fees? Names can repeat. So give each row a unique number, the admission number. Now each Riya is different. Every row needs a unique value. That column is called a key.

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)

More KwickClips from this lesson

Candidate key table marking AdmNo and Email as unique and Name as not.What is a candidate key?38 secAdmNo marked primary and Email marked alternate key.What is an alternate key?37 secFEES table pointing to STUDENT through the admission number.What is a foreign key?41 sec
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