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 normalization? Explain 1NF, 2NF and 3NF.
Normalization organises tables so each fact is stored once. 1NF means single values per cell, 2NF removes columns that depend on only part of a composite key, and 3NF removes columns that depend on other non-key columns.
IntermediateIn-depth2 min read - What is the difference between ROW_NUMBER, RANK and DENSE_RANK?
All three number rows in a given order. ROW_NUMBER always gives unique numbers 1, 2, 3, even for ties. RANK gives tied rows the same number and then skips ahead (1, 2, 2, 4). DENSE_RANK gives tied rows the same number without skipping (1, 2, 2, 3).
IntermediateIn-depth4 min read