169 lines
4.9 KiB
Markdown
169 lines
4.9 KiB
Markdown
---
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{
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"title": "GROUP BY",
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"language": "en"
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}
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---
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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# GROUP BY
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## description
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GROUP BY `GROUPING SETS` ｜ `CUBE` ｜ `ROLLUP` is an extension to GROUP BY clause. This syntax lets you define multiple groupings in the same query. GROUPING SETS produce a single result set that is equivalent to a UNION ALL of differently grouped rows
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For example GROUPING SETS clause:
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```
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SELECT a, b, SUM( c ) FROM tab1 GROUP BY GROUPING SETS ( (a, b), (a), (b), ( ) );
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```
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This statement is equivalent to:
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```
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SELECT a, b, SUM( c ) FROM tab1 GROUP BY a, b
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UNION
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SELECT a, null, SUM( c ) FROM tab1 GROUP BY a
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UNION
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SELECT null, b, SUM( c ) FROM tab1 GROUP BY b
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UNION
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SELECT null, null, SUM( c ) FROM tab1
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```
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`GROUPING(expr)` indicates whether a specified column expression in a GROUP BY list is aggregated or not. GROUPING returns 1 for aggregated or 0 for not aggregated in the result set.
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`GROUPING_ID(expr [ , expr [ , ... ] ])` describes which of a list of expressions are grouped in a row produced by a GROUP BY query. The GROUPING_ID function simply returns the decimal equivalent of the binary value formed as a result of the concatenation of the values returned by the GROUPING functions.
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### Syntax
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```
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SELECT ...
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FROM ...
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[ ... ]
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GROUP BY [
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, ... |
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GROUPING SETS [, ...] ( groupSet [ , groupSet [ , ... ] ] ) |
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ROLLUP(expr [ , expr [ , ... ] ]) |
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expr [ , expr [ , ... ] ] WITH ROLLUP |
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CUBE(expr [ , expr [ , ... ] ]) |
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expr [ , expr [ , ... ] ] WITH CUBE
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]
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[ ... ]
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```
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### Parameters
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`groupSet` is a set of expression or column or it's alias appearing in the query block’s SELECT list. `groupSet ::= { ( expr [ , expr [ , ... ] ] )}`
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`expr` is expression or column or it's alias appearing in the query block’s SELECT list.
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### Note
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doris supports PostgreSQL like syntax, for example:
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```
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SELECT a, b, SUM( c ) FROM tab1 GROUP BY GROUPING SETS ( (a, b), (a), (b), ( ) );
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SELECT a, b,c, SUM( d ) FROM tab1 GROUP BY ROLLUP(a,b,c)
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SELECT a, b,c, SUM( d ) FROM tab1 GROUP BY CUBE(a,b,c)
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```
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`ROLLUP(a,b,c)` is equivalent to `GROUPING SETS` as follows:
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```
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GROUPING SETS (
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(a,b,c),
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( a, b ),
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( a),
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( )
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)
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```
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`CUBE ( a, b, c )` is equivalent to `GROUPING SETS` as follows:
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```
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GROUPING SETS (
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( a, b, c ),
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( a, b ),
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( a, c ),
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( a ),
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( b, c ),
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( b ),
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( c ),
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( )
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)
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```
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## example
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This is a simple example
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```
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> SELECT * FROM t;
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+------+------+------+
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| k1 | k2 | k3 |
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+------+------+------+
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| a | A | 1 |
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| a | A | 2 |
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| a | B | 1 |
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| a | B | 3 |
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| b | A | 1 |
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| b | A | 4 |
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| b | B | 1 |
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| b | B | 5 |
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+------+------+------+
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8 rows in set (0.01 sec)
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> SELECT k1, k2, SUM(k3) FROM t GROUP BY GROUPING SETS ( (k1, k2), (k2), (k1), ( ) );
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+------+------+-----------+
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| k1 | k2 | sum(`k3`) |
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+------+------+-----------+
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| b | B | 6 |
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| a | B | 4 |
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| a | A | 3 |
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| b | A | 5 |
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| NULL | B | 10 |
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| NULL | A | 8 |
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| a | NULL | 7 |
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| b | NULL | 11 |
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| NULL | NULL | 18 |
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+------+------+-----------+
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9 rows in set (0.06 sec)
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> SELECT k1, k2, GROUPING_ID(k1,k2), SUM(k3) FROM t GROUP BY GROUPING SETS ((k1, k2), (k1), (k2), ());
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+------+------+---------------+----------------+
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| k1 | k2 | grouping_id(k1,k2) | sum(`k3`) |
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+------+------+---------------+----------------+
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| a | A | 0 | 3 |
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| a | B | 0 | 4 |
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| a | NULL | 1 | 7 |
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| b | A | 0 | 5 |
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| b | B | 0 | 6 |
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| b | NULL | 1 | 11 |
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| NULL | A | 2 | 8 |
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| NULL | B | 2 | 10 |
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| NULL | NULL | 3 | 18 |
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+------+------+---------------+----------------+
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9 rows in set (0.02 sec)
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```
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## keyword
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GROUP, GROUPING, GROUPING_ID, GROUPING_SETS, GROUPING SETS, CUBE, ROLLUP
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