The GROUP BY clause groups the rows, but it does not necessarily sort the

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Asked: June 10, 20262026-06-10T12:01:30+00:00 2026-06-10T12:01:30+00:00

The GROUP BY clause groups the rows, but it does not necessarily sort the

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The GROUP BY clause groups the rows, but it does not necessarily sort the results in any particular order. To change the order, use the ORDER BY clause, which follows the GROUP BY clause. The columns used in the ORDER BY clause must appear in the SELECT list, which is unlike the normal use of ORDER BY. [Oracle by Example, fourth Edition, page 274]

Why is that? Why does using GROUP BY influence the required columns in the SELECT clause?

Also, in the case where I do not use GROUP BY: Why would I want to ORDER BY some columns but then select only a subset of the columns?

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1 Answer

Editorial Team · Answer 1 · 2026-06-10T12:01:32+00:00

Actually the statement is not entirely true as Dave Costa’s example shows.

The Oracle documentation says that an expression can be used but the expression must be based on the columns in the selection list.

expr – expr orders rows based on their value for expr. The expression is based on
columns in the select list or columns in the tables, views, or materialized views in the
FROM clause. Source: Oracle® Database
SQL Language Reference
11g Release 2 (11.2)
E26088-01
September 2011. Page 19-33

From the the same work page 19-13 and 19-33 (Page 1355 and 1365 in the PDF)

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