| --- |
| { |
| "title": "MAP_AGG", |
| "language": "en" |
| } |
| --- |
| |
| <!-- |
| Licensed to the Apache Software Foundation (ASF) under one |
| or more contributor license agreements. See the NOTICE file |
| distributed with this work for additional information |
| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, |
| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| KIND, either express or implied. See the License for the |
| specific language governing permissions and limitations |
| under the License. |
| --> |
| |
| ## MAP_AGG |
| ### description |
| #### Syntax |
| |
| `MAP_AGG(expr1, expr2)` |
| |
| |
| Returns a map consists of expr1 as the key and expr2 as the corresponding value. |
| |
| ### example |
| ``` |
| MySQL > select `n_nationkey`, `n_name`, `n_regionkey` from `nation`; |
| +-------------+----------------+-------------+ |
| | n_nationkey | n_name | n_regionkey | |
| +-------------+----------------+-------------+ |
| | 0 | ALGERIA | 0 | |
| | 1 | ARGENTINA | 1 | |
| | 2 | BRAZIL | 1 | |
| | 3 | CANADA | 1 | |
| | 4 | EGYPT | 4 | |
| | 5 | ETHIOPIA | 0 | |
| | 6 | FRANCE | 3 | |
| | 7 | GERMANY | 3 | |
| | 8 | INDIA | 2 | |
| | 9 | INDONESIA | 2 | |
| | 10 | IRAN | 4 | |
| | 11 | IRAQ | 4 | |
| | 12 | JAPAN | 2 | |
| | 13 | JORDAN | 4 | |
| | 14 | KENYA | 0 | |
| | 15 | MOROCCO | 0 | |
| | 16 | MOZAMBIQUE | 0 | |
| | 17 | PERU | 1 | |
| | 18 | CHINA | 2 | |
| | 19 | ROMANIA | 3 | |
| | 20 | SAUDI ARABIA | 4 | |
| | 21 | VIETNAM | 2 | |
| | 22 | RUSSIA | 3 | |
| | 23 | UNITED KINGDOM | 3 | |
| | 24 | UNITED STATES | 1 | |
| +-------------+----------------+-------------+ |
| |
| MySQL > select `n_regionkey`, map_agg(`n_nationkey`, `n_name`) from `nation` group by `n_regionkey`; |
| +-------------+---------------------------------------------------------------------------+ |
| | n_regionkey | map_agg(`n_nationkey`, `n_name`) | |
| +-------------+---------------------------------------------------------------------------+ |
| | 1 | {1:"ARGENTINA", 2:"BRAZIL", 3:"CANADA", 17:"PERU", 24:"UNITED STATES"} | |
| | 0 | {0:"ALGERIA", 5:"ETHIOPIA", 14:"KENYA", 15:"MOROCCO", 16:"MOZAMBIQUE"} | |
| | 3 | {6:"FRANCE", 7:"GERMANY", 19:"ROMANIA", 22:"RUSSIA", 23:"UNITED KINGDOM"} | |
| | 4 | {4:"EGYPT", 10:"IRAN", 11:"IRAQ", 13:"JORDAN", 20:"SAUDI ARABIA"} | |
| | 2 | {8:"INDIA", 9:"INDONESIA", 12:"JAPAN", 18:"CHINA", 21:"VIETNAM"} | |
| +-------------+---------------------------------------------------------------------------+ |
| |
| MySQL > select n_regionkey, map_agg(`n_name`, `n_nationkey` % 5) from `nation` group by `n_regionkey`; |
| +-------------+------------------------------------------------------------------------+ |
| | n_regionkey | map_agg(`n_name`, (`n_nationkey` % 5)) | |
| +-------------+------------------------------------------------------------------------+ |
| | 2 | {"INDIA":3, "INDONESIA":4, "JAPAN":2, "CHINA":3, "VIETNAM":1} | |
| | 0 | {"ALGERIA":0, "ETHIOPIA":0, "KENYA":4, "MOROCCO":0, "MOZAMBIQUE":1} | |
| | 3 | {"FRANCE":1, "GERMANY":2, "ROMANIA":4, "RUSSIA":2, "UNITED KINGDOM":3} | |
| | 1 | {"ARGENTINA":1, "BRAZIL":2, "CANADA":3, "PERU":2, "UNITED STATES":4} | |
| | 4 | {"EGYPT":4, "IRAN":0, "IRAQ":1, "JORDAN":3, "SAUDI ARABIA":0} | |
| +-------------+------------------------------------------------------------------------+ |
| ``` |
| ### keywords |
| MAP_AGG |
