On 2/21/21 3:06 PM, e...@xs4all.nl wrote:
>> On 2021.02.21. 13:52 Vik Fearing <v...@postgresfriends.org> wrote:
>>
>> Attached is a patch to implement this for PostgreSQL.
>> []
>
> The changed line that gets stuffed into sql_features is missing a terminal
> value (to fill the 'comments' column).
> This line:
> '+T434 GROUP BY DISTINCT YES'
>
> (A tab at the end will do, I suppose; that's how I fixed the patch locally)
Argh. Fixed.
Thank you for looking at it!
--
Vik Fearing
>From d5587ece129fbaf4309ddf48d44b9d0249d9cf56 Mon Sep 17 00:00:00 2001
From: Vik Fearing <v...@postgresfriends.org>
Date: Sun, 21 Feb 2021 10:26:57 +0100
Subject: [PATCH] implement GROUP BY DISTINCT
---
doc/src/sgml/queries.sgml | 41 ++++++++
doc/src/sgml/ref/select.sgml | 9 +-
src/backend/catalog/sql_features.txt | 2 +-
src/backend/nodes/copyfuncs.c | 2 +
src/backend/nodes/equalfuncs.c | 2 +
src/backend/nodes/list.c | 16 +++
src/backend/nodes/outfuncs.c | 2 +
src/backend/nodes/readfuncs.c | 1 +
src/backend/optimizer/plan/planner.c | 2 +-
src/backend/parser/analyze.c | 1 +
src/backend/parser/gram.y | 22 ++--
src/backend/parser/parse_agg.c | 58 ++++++++++-
src/include/nodes/parsenodes.h | 2 +
src/include/nodes/pg_list.h | 1 +
src/include/parser/parse_agg.h | 2 +-
src/test/regress/expected/groupingsets.out | 111 +++++++++++++++++++++
src/test/regress/sql/groupingsets.sql | 26 +++++
17 files changed, 284 insertions(+), 16 deletions(-)
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml
index 4741506eb5..3c8facff87 100644
--- a/doc/src/sgml/queries.sgml
+++ b/doc/src/sgml/queries.sgml
@@ -1372,6 +1372,47 @@ GROUP BY GROUPING SETS (
</programlisting>
</para>
+ <para>
+ When specifying multiple grouping items together, the final set of grouping
+ sets might contain duplicates. For example:
+<programlisting>
+GROUP BY ROLLUP (a, b), ROLLUP (a, c)
+</programlisting>
+ is equivalent to
+<programlisting>
+GROUP BY GROUPING SETS (
+ (a, b, c),
+ (a, b),
+ (a, b),
+ (a, c),
+ (a),
+ (a),
+ (a, c),
+ (a),
+ ()
+)
+</programlisting>
+ If these duplicates are undesirable, they can be removed using the
+ <literal>DISTINCT</literal> clause directly on the <literal>GROUP BY</literal>.
+ Therefore:
+<programlisting>
+GROUP BY <emphasis>DISTINCT</emphasis> ROLLUP (a, b), ROLLUP (a, c)
+</programlisting>
+ is equivalent to
+<programlisting>
+GROUP BY GROUPING SETS (
+ (a, b, c),
+ (a, b),
+ (a, c),
+ (a),
+ ()
+)
+</programlisting>
+ This is not the same as using <literal>SELECT DISTINCT</literal> because the output
+ rows may still contain duplicates. If any of the ungrouped columns contains NULL,
+ it will be indistiguishable from the NULL used when that same column is grouped.
+ </para>
+
<note>
<para>
The construct <literal>(a, b)</literal> is normally recognized in expressions as
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index eb8b524951..0e2b2bef49 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -37,7 +37,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ * | <replaceable class="parameter">expression</replaceable> [ [ AS ] <replaceable class="parameter">output_name</replaceable> ] [, ...] ]
[ FROM <replaceable class="parameter">from_item</replaceable> [, ...] ]
[ WHERE <replaceable class="parameter">condition</replaceable> ]
- [ GROUP BY <replaceable class="parameter">grouping_element</replaceable> [, ...] ]
+ [ GROUP BY [ ALL | DISTINCT ] <replaceable class="parameter">grouping_element</replaceable> [, ...] ]
[ HAVING <replaceable class="parameter">condition</replaceable> ]
[ WINDOW <replaceable class="parameter">window_name</replaceable> AS ( <replaceable class="parameter">window_definition</replaceable> ) [, ...] ]
[ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] <replaceable class="parameter">select</replaceable> ]
@@ -776,7 +776,7 @@ WHERE <replaceable class="parameter">condition</replaceable>
<para>
The optional <literal>GROUP BY</literal> clause has the general form
<synopsis>
-GROUP BY <replaceable class="parameter">grouping_element</replaceable> [, ...]
+GROUP BY [ ALL | DISTINCT ] <replaceable class="parameter">grouping_element</replaceable> [, ...]
</synopsis>
</para>
@@ -800,7 +800,10 @@ GROUP BY <replaceable class="parameter">grouping_element</replaceable> [, ...]
independent <replaceable>grouping sets</replaceable>. The effect of this is
equivalent to constructing a <literal>UNION ALL</literal> between
subqueries with the individual grouping sets as their
- <literal>GROUP BY</literal> clauses. For further details on the handling
+ <literal>GROUP BY</literal> clauses. The optional <literal>DISTINCT</literal>
+ clause removes duplicate sets before processing; it does <emphasis>not</emphasis>
+ transform the <literal>UNION ALL</literal> into a <literal>UNION DISTINCT</literal>.
+ For further details on the handling
of grouping sets see <xref linkend="queries-grouping-sets"/>.
</para>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index a24387c1e7..2e111ba755 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -481,7 +481,7 @@ T351 Bracketed SQL comments (/*...*/ comments) YES
T431 Extended grouping capabilities YES
T432 Nested and concatenated GROUPING SETS YES
T433 Multiargument GROUPING function YES
-T434 GROUP BY DISTINCT NO
+T434 GROUP BY DISTINCT YES
T441 ABS and MOD functions YES
T461 Symmetric BETWEEN predicate YES
T471 Result sets return value NO
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 65bbc18ecb..9be432ea7b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3113,6 +3113,7 @@ _copyQuery(const Query *from)
COPY_NODE_FIELD(onConflict);
COPY_NODE_FIELD(returningList);
COPY_NODE_FIELD(groupClause);
+ COPY_SCALAR_FIELD(groupDistinct);
COPY_NODE_FIELD(groupingSets);
COPY_NODE_FIELD(havingQual);
COPY_NODE_FIELD(windowClause);
@@ -3199,6 +3200,7 @@ _copySelectStmt(const SelectStmt *from)
COPY_NODE_FIELD(fromClause);
COPY_NODE_FIELD(whereClause);
COPY_NODE_FIELD(groupClause);
+ COPY_SCALAR_FIELD(groupDistinct);
COPY_NODE_FIELD(havingClause);
COPY_NODE_FIELD(windowClause);
COPY_NODE_FIELD(valuesLists);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index c2d73626fc..bc5e9e52fe 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -977,6 +977,7 @@ _equalQuery(const Query *a, const Query *b)
COMPARE_NODE_FIELD(onConflict);
COMPARE_NODE_FIELD(returningList);
COMPARE_NODE_FIELD(groupClause);
+ COMPARE_SCALAR_FIELD(groupDistinct);
COMPARE_NODE_FIELD(groupingSets);
COMPARE_NODE_FIELD(havingQual);
COMPARE_NODE_FIELD(windowClause);
@@ -1053,6 +1054,7 @@ _equalSelectStmt(const SelectStmt *a, const SelectStmt *b)
COMPARE_NODE_FIELD(fromClause);
COMPARE_NODE_FIELD(whereClause);
COMPARE_NODE_FIELD(groupClause);
+ COMPARE_SCALAR_FIELD(groupDistinct);
COMPARE_NODE_FIELD(havingClause);
COMPARE_NODE_FIELD(windowClause);
COMPARE_NODE_FIELD(valuesLists);
diff --git a/src/backend/nodes/list.c b/src/backend/nodes/list.c
index dbf6b30233..94fb236daf 100644
--- a/src/backend/nodes/list.c
+++ b/src/backend/nodes/list.c
@@ -1506,6 +1506,22 @@ list_sort(List *list, list_sort_comparator cmp)
qsort(list->elements, len, sizeof(ListCell), (qsort_comparator) cmp);
}
+/*
+ * list_sort comparator for sorting a list into ascending int order.
+ */
+int
+list_int_cmp(const ListCell *p1, const ListCell *p2)
+{
+ int v1 = lfirst_int(p1);
+ int v2 = lfirst_int(p2);
+
+ if (v1 < v2)
+ return -1;
+ if (v1 > v2)
+ return 1;
+ return 0;
+}
+
/*
* list_sort comparator for sorting a list into ascending OID order.
*/
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index f5dcedf6e8..7c7ef697f9 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2758,6 +2758,7 @@ _outSelectStmt(StringInfo str, const SelectStmt *node)
WRITE_NODE_FIELD(fromClause);
WRITE_NODE_FIELD(whereClause);
WRITE_NODE_FIELD(groupClause);
+ WRITE_BOOL_FIELD(groupDistinct);
WRITE_NODE_FIELD(havingClause);
WRITE_NODE_FIELD(windowClause);
WRITE_NODE_FIELD(valuesLists);
@@ -2983,6 +2984,7 @@ _outQuery(StringInfo str, const Query *node)
WRITE_NODE_FIELD(onConflict);
WRITE_NODE_FIELD(returningList);
WRITE_NODE_FIELD(groupClause);
+ WRITE_BOOL_FIELD(groupDistinct);
WRITE_NODE_FIELD(groupingSets);
WRITE_NODE_FIELD(havingQual);
WRITE_NODE_FIELD(windowClause);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 4388aae71d..0bc9429d67 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -271,6 +271,7 @@ _readQuery(void)
READ_NODE_FIELD(onConflict);
READ_NODE_FIELD(returningList);
READ_NODE_FIELD(groupClause);
+ READ_BOOL_FIELD(groupDistinct);
READ_NODE_FIELD(groupingSets);
READ_NODE_FIELD(havingQual);
READ_NODE_FIELD(windowClause);
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index adf68d8790..66bad90f60 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2427,7 +2427,7 @@ preprocess_grouping_sets(PlannerInfo *root)
ListCell *lc_set;
grouping_sets_data *gd = palloc0(sizeof(grouping_sets_data));
- parse->groupingSets = expand_grouping_sets(parse->groupingSets, -1);
+ parse->groupingSets = expand_grouping_sets(parse->groupingSets, parse->groupDistinct, -1);
gd->any_hashable = false;
gd->unhashable_refs = NULL;
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 0f3a70c49a..7149724953 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -1264,6 +1264,7 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
qry->sortClause,
EXPR_KIND_GROUP_BY,
false /* allow SQL92 rules */ );
+ qry->groupDistinct = stmt->groupDistinct;
if (stmt->distinctClause == NIL)
{
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index dd72a9fc3c..66e5401684 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -443,7 +443,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <node> for_locking_item
%type <list> for_locking_clause opt_for_locking_clause for_locking_items
%type <list> locked_rels_list
-%type <boolean> all_or_distinct
+%type <boolean> all_or_distinct distinct_or_all
%type <node> join_qual
%type <jtype> join_type
@@ -11294,7 +11294,8 @@ simple_select:
n->intoClause = $4;
n->fromClause = $5;
n->whereClause = $6;
- n->groupClause = $7;
+ n->groupClause = linitial($7);
+ n->groupDistinct = (bool) intVal(lsecond($7));
n->havingClause = $8;
n->windowClause = $9;
$$ = (Node *)n;
@@ -11309,7 +11310,8 @@ simple_select:
n->intoClause = $4;
n->fromClause = $5;
n->whereClause = $6;
- n->groupClause = $7;
+ n->groupClause = linitial($7);
+ n->groupDistinct = (bool) intVal(lsecond($7));
n->havingClause = $8;
n->windowClause = $9;
$$ = (Node *)n;
@@ -11531,12 +11533,19 @@ opt_table: TABLE
| /*EMPTY*/
;
+/* The difference between these two is the default */
all_or_distinct:
ALL { $$ = true; }
| DISTINCT { $$ = false; }
| /*EMPTY*/ { $$ = false; }
;
+distinct_or_all:
+ DISTINCT { $$ = true; }
+ | ALL { $$ = false; }
+ | /*EMPTY*/ { $$ = false; }
+ ;
+
/* We use (NIL) as a placeholder to indicate that all target expressions
* should be placed in the DISTINCT list during parsetree analysis.
*/
@@ -11760,8 +11769,8 @@ first_or_next: FIRST_P { $$ = 0; }
* GroupingSet node of some type.
*/
group_clause:
- GROUP_P BY group_by_list { $$ = $3; }
- | /*EMPTY*/ { $$ = NIL; }
+ GROUP_P BY distinct_or_all group_by_list { $$ = list_make2($4, makeInteger((int) $3)); }
+ | /*EMPTY*/ { $$ = list_make2(NIL, makeInteger((int) false)); }
;
group_by_list:
@@ -15134,7 +15143,8 @@ PLpgSQL_Expr: opt_distinct_clause opt_target_list
n->targetList = $2;
n->fromClause = $3;
n->whereClause = $4;
- n->groupClause = $5;
+ n->groupClause = linitial($5);
+ n->groupDistinct = (bool) intVal(lsecond($5));
n->havingClause = $6;
n->windowClause = $7;
n->sortClause = $8;
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index fd08b9eeff..899327aaf4 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -1071,7 +1071,7 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
* The limit of 4096 is arbitrary and exists simply to avoid resource
* issues from pathological constructs.
*/
- List *gsets = expand_grouping_sets(qry->groupingSets, 4096);
+ List *gsets = expand_grouping_sets(qry->groupingSets, qry->groupDistinct, 4096);
if (!gsets)
ereport(ERROR,
@@ -1735,6 +1735,33 @@ cmp_list_len_asc(const ListCell *a, const ListCell *b)
return (la > lb) ? 1 : (la == lb) ? 0 : -1;
}
+/* list_sort comparator to sort sub-lists by length and contents */
+static int
+cmp_list_len_contents_asc(const ListCell *a, const ListCell *b)
+{
+ int res = cmp_list_len_asc(a, b);
+
+ if (res == 0)
+ {
+ List *la = (List *) lfirst(a);
+ List *lb = (List *) lfirst(b);
+ ListCell *lca;
+ ListCell *lcb;
+
+ forboth(lca, la, lcb, lb)
+ {
+ int va = intVal(lca);
+ int vb = intVal(lcb);
+ if (va > vb)
+ return 1;
+ if (va < vb)
+ return -1;
+ }
+ }
+
+ return res;
+}
+
/*
* Expand a groupingSets clause to a flat list of grouping sets.
* The returned list is sorted by length, shortest sets first.
@@ -1743,7 +1770,7 @@ cmp_list_len_asc(const ListCell *a, const ListCell *b)
* some consistency checks.
*/
List *
-expand_grouping_sets(List *groupingSets, int limit)
+expand_grouping_sets(List *groupingSets, bool groupDistinct, int limit)
{
List *expanded_groups = NIL;
List *result = NIL;
@@ -1801,8 +1828,31 @@ expand_grouping_sets(List *groupingSets, int limit)
result = new_result;
}
- /* Now sort the lists by length */
- list_sort(result, cmp_list_len_asc);
+ /* Now sort the lists by length and deduplicate if necessary */
+ if (!groupDistinct || list_length(result) < 2)
+ list_sort(result, cmp_list_len_asc);
+ else
+ {
+ ListCell *cell;
+ List *prev;
+
+ /* Sort each groupset individually */
+ foreach(cell, result)
+ list_sort(lfirst(cell), list_int_cmp);
+
+ /* Now sort the list of groupsets by length and contents */
+ list_sort(result, cmp_list_len_contents_asc);
+
+ /* Finally, remove duplicates */
+ prev = list_nth_node(List, result, 0);
+ for_each_from(cell, result, 1)
+ {
+ if (equal(lfirst(cell), prev))
+ foreach_delete_current(result, cell);
+ else
+ prev = lfirst(cell);
+ }
+ }
return result;
}
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 236832a2ca..5af9f6bd9d 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -146,6 +146,7 @@ typedef struct Query
List *returningList; /* return-values list (of TargetEntry) */
List *groupClause; /* a list of SortGroupClause's */
+ bool groupDistinct; /* is the group by clause distinct? */
List *groupingSets; /* a list of GroupingSet's if present */
@@ -1629,6 +1630,7 @@ typedef struct SelectStmt
List *fromClause; /* the FROM clause */
Node *whereClause; /* WHERE qualification */
List *groupClause; /* GROUP BY clauses */
+ bool groupDistinct; /* Is this GROUP BY DISTINCT? */
Node *havingClause; /* HAVING conditional-expression */
List *windowClause; /* WINDOW window_name AS (...), ... */
diff --git a/src/include/nodes/pg_list.h b/src/include/nodes/pg_list.h
index 404e03f132..30f98c4595 100644
--- a/src/include/nodes/pg_list.h
+++ b/src/include/nodes/pg_list.h
@@ -604,6 +604,7 @@ extern pg_nodiscard List *list_copy_deep(const List *oldlist);
typedef int (*list_sort_comparator) (const ListCell *a, const ListCell *b);
extern void list_sort(List *list, list_sort_comparator cmp);
+extern int list_int_cmp(const ListCell *p1, const ListCell *p2);
extern int list_oid_cmp(const ListCell *p1, const ListCell *p2);
#endif /* PG_LIST_H */
diff --git a/src/include/parser/parse_agg.h b/src/include/parser/parse_agg.h
index 0a2546c3ea..4dea01752a 100644
--- a/src/include/parser/parse_agg.h
+++ b/src/include/parser/parse_agg.h
@@ -26,7 +26,7 @@ extern void transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
extern void parseCheckAggregates(ParseState *pstate, Query *qry);
-extern List *expand_grouping_sets(List *groupingSets, int limit);
+extern List *expand_grouping_sets(List *groupingSets, bool groupDistinct, int limit);
extern int get_aggregate_argtypes(Aggref *aggref, Oid *inputTypes);
diff --git a/src/test/regress/expected/groupingsets.out b/src/test/regress/expected/groupingsets.out
index 7c844c6e09..4c467c1b15 100644
--- a/src/test/regress/expected/groupingsets.out
+++ b/src/test/regress/expected/groupingsets.out
@@ -1929,4 +1929,115 @@ set work_mem to default;
drop table gs_group_1;
drop table gs_hash_1;
+-- GROUP BY DISTINCT
+-- "normal" behavior...
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by all rollup(a, b), rollup(a, c)
+order by a, b, c;
+ a | b | c
+---+---+---
+ 1 | 2 | 3
+ 1 | 2 |
+ 1 | 2 |
+ 1 | | 3
+ 1 | | 3
+ 1 | |
+ 1 | |
+ 1 | |
+ 4 | | 6
+ 4 | | 6
+ 4 | | 6
+ 4 | |
+ 4 | |
+ 4 | |
+ 4 | |
+ 4 | |
+ 7 | 8 | 9
+ 7 | 8 |
+ 7 | 8 |
+ 7 | | 9
+ 7 | | 9
+ 7 | |
+ 7 | |
+ 7 | |
+ | |
+(25 rows)
+
+-- ...which is also the default
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by rollup(a, b), rollup(a, c)
+order by a, b, c;
+ a | b | c
+---+---+---
+ 1 | 2 | 3
+ 1 | 2 |
+ 1 | 2 |
+ 1 | | 3
+ 1 | | 3
+ 1 | |
+ 1 | |
+ 1 | |
+ 4 | | 6
+ 4 | | 6
+ 4 | | 6
+ 4 | |
+ 4 | |
+ 4 | |
+ 4 | |
+ 4 | |
+ 7 | 8 | 9
+ 7 | 8 |
+ 7 | 8 |
+ 7 | | 9
+ 7 | | 9
+ 7 | |
+ 7 | |
+ 7 | |
+ | |
+(25 rows)
+
+-- "group by distinct" behavior...
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by distinct rollup(a, b), rollup(a, c)
+order by a, b, c;
+ a | b | c
+---+---+---
+ 1 | 2 | 3
+ 1 | 2 |
+ 1 | | 3
+ 1 | |
+ 4 | | 6
+ 4 | | 6
+ 4 | |
+ 4 | |
+ 7 | 8 | 9
+ 7 | 8 |
+ 7 | | 9
+ 7 | |
+ | |
+(13 rows)
+
+-- ...which is not the same as "select distinct"
+select distinct a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by rollup(a, b), rollup(a, c)
+order by a, b, c;
+ a | b | c
+---+---+---
+ 1 | 2 | 3
+ 1 | 2 |
+ 1 | | 3
+ 1 | |
+ 4 | | 6
+ 4 | |
+ 7 | 8 | 9
+ 7 | 8 |
+ 7 | | 9
+ 7 | |
+ | |
+(11 rows)
+
-- end
diff --git a/src/test/regress/sql/groupingsets.sql b/src/test/regress/sql/groupingsets.sql
index 18ae803e9d..3944944704 100644
--- a/src/test/regress/sql/groupingsets.sql
+++ b/src/test/regress/sql/groupingsets.sql
@@ -529,4 +529,30 @@ set work_mem to default;
drop table gs_group_1;
drop table gs_hash_1;
+-- GROUP BY DISTINCT
+
+-- "normal" behavior...
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by all rollup(a, b), rollup(a, c)
+order by a, b, c;
+
+-- ...which is also the default
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by rollup(a, b), rollup(a, c)
+order by a, b, c;
+
+-- "group by distinct" behavior...
+select a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by distinct rollup(a, b), rollup(a, c)
+order by a, b, c;
+
+-- ...which is not the same as "select distinct"
+select distinct a, b, c
+from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
+group by rollup(a, b), rollup(a, c)
+order by a, b, c;
+
-- end
--
2.25.1
