Project: Apache Spark (App Definition and Development / Streaming & Messaging)
File: sql-ref-syntax-qry-select-unpivot.md

layout: global title: UNPIVOT Clause displayTitle: UNPIVOT Clause license: | 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. The `UNPIVOT` clause transforms multiple columns into multiple rows used in `SELECT` clause. The `UNPIVOT` clause can be specified after the table name or subquery. ```sql UNPIVOT [ { INCLUDE | EXCLUDE } NULLS ] ( { singlevaluecolumnunpivot | multivaluecolumnunpivot } ) [[AS] alias] singlevaluecolumn_unpivot: values_column FOR name_column IN (unpivot_column [[AS] alias] [, ...]) multivaluecolumn_unpivot: (values_column [, ...]) FOR name_column IN ((unpivot_column [, ...]) [[AS] alias] [, ...]) ``` unpivot_column* Contains columns in the `FROM` clause, which specifies the columns we want to unpivot. name_column* The name for the column that holds the names of the unpivoted columns. values_column* The name for the column that holds the values of the unpivoted

```sql CREATE TABLE sales_quarterly (year INT, q1 INT, q2 INT, q3 INT, q4 INT); INSERT INTO sales_quarterly VALUES (2020, null, 1000, 2000, 2500), (2021, 2250, 3200, 4200, 5900), (2022, 4200, 3100, null, null); -- column names are used as unpivot columns SELECT * FROM sales_quarterly UNPIVOT ( sales FOR quarter IN (q1, q2, q3, q4) ); +++-+ | year | quarter | sales | +++-+ | 2020 | q2 | 1000 | | 2020 | q3 | 2000 | | 2020 | q4 | 2500 | | 2021 | q1 | 2250 | | 2021 | q2 | 3200 | | 2021 | q3 | 4200 | | 2021 | q4 | 5900 | | 2022 | q1 | 4200 | | 2022 | q2 | 3100 | +++-+ -- NULL values are excluded by default, they can be included -- unpivot columns can be alias -- unpivot result can be referenced via its alias SELECT up.* FROM sales_quarterly UNPIVOT INCLUDE NULLS ( sales FOR quarter IN (q1 AS Q1, q2 AS Q2, q3 AS Q3, q4 AS Q4) ) AS up; +++-+ | year | quarter | sales | +++-+ | 2020 | Q1 | NULL | | 2020 | Q2 | 1000 | | 2020 | Q3 | 2000 | | 2020 | Q4 | 2500 | | 2021 | Q1 | 2250 | | 2021 | Q2 | 3200 | | 2021 | Q3 | 4200 | | 2021 | Q4 | 5900 | | 2022 | Q1 | 4200 | | 2022 | Q2 | 3100 | | 2022 | Q3 | NULL | | 2022 | Q4 | NULL | +++-+ -- multiple value columns can be unpivoted per row SELECT * FROM sales_quarterly UNPIVOT EXCLUDE NULLS ( (firstquarter, secondquarter) FOR halfofthe_year IN ( (q1, q2) AS H1, (q3, q4) AS H2 ) ); ++++-+ | id | halfoftheyear | firstquarter | second_quarter | ++++-+ | 2020 | H1 | NULL | 1000 | | 2020 | H2 | 2000 | 2500 | | 2021 | H1 | 2250 | 3200 | | 2021 | H2 | 4200 | 5900 | | 2022 | H1 | 4200 | 3100 | ++++-+ ```