GROUP BY and Aggregate Functions: HAVING, Conditional Aggregation, GROUPING SETS and ROLLUP
GROUP BY collapses rows into groups, aggregates ignore NULL, and in SQL Server AVG over an integer column returns an integer. We show COUNT(*) versus COUNT(column), where WHERE and HAVING belong, STRING_AGG, conditional aggregation with CASE, a PIVOT comparison, and ROLLUP, CUBE, GROUPING SETS with GROUPING() on Bookstore data with real output.
8 Nov 2026
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14 min
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4
