Does the order of columns matter in a group by clause?

Question

If I have two columns, one with very high cardinality and one with very low cardinality (unique # of values), does it matter in which order I group by?

Here\'s an ex

Answer 1

There's a legacy, non-standard feature of Microsoft SQL Server called ROLLUP. ROLLUP is an extension to the GROUP BY syntax and when it is used the order of the GROUP BY columns determines which columns should be grouped in the result. ROLLUP is deprecated however. The standard SQL alternative is to use grouping sets, which is supported by SQL Server 2008 and later versions.