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 the difference between a unique index and a primary key?
Both enforce uniqueness and create an index. A primary key also forbids NULL, there is only one per table, and it identifies each row. A table can have many unique indexes, and they usually allow NULLs.
BeginnerQuick answer1 min read