Interview Q&A / SQL & DBMS
SQL & DBMS interview questions
Joins, keys, normalisation, indexes and transactions for placement and backend interviews.
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- What is a composite key and when do you need one?
A composite key is a key made of two or more columns that together identify a row. It is needed when no single column is unique, such as a student and subject pair in a marks table.
BeginnerQuick answer1 min read