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 COUNT(*), COUNT(column) and COUNT(DISTINCT column)?
COUNT(*) counts all rows, COUNT(column) counts rows where that column is not NULL, and COUNT(DISTINCT column) counts the different non-NULL values.
BeginnerQuick answer1 min read