8de43338be
### What changes were proposed in this pull request? update sql-ref docs, the following key words will be added in this PR. CASE/ELSE WHEN/THEN MAP KEYS TERMINATED BY NULL DEFINED AS LINES TERMINATED BY ESCAPED BY COLLECTION ITEMS TERMINATED BY PIVOT LATERAL VIEW OUTER? ROW FORMAT SERDE ROW FORMAT DELIMITED FIELDS TERMINATED BY IGNORE NULLS FIRST LAST ### Why are the changes needed? let more users know the sql key words usage ### Does this PR introduce _any_ user-facing change?     ### How was this patch tested? No Closes #29056 from GuoPhilipse/add-missing-keywords. Lead-authored-by: GuoPhilipse <guofei_ok@126.com> Co-authored-by: GuoPhilipse <46367746+GuoPhilipse@users.noreply.github.com> Signed-off-by: Takeshi Yamamuro <yamamuro@apache.org>
110 lines
4.3 KiB
Markdown
110 lines
4.3 KiB
Markdown
---
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layout: global
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title: CASE Clause
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displayTitle: CASE Clause
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license: |
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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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, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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---
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### Description
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`CASE` clause uses a rule to return a specific result based on the specified condition, similar to if/else statements in other programming languages.
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### Syntax
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```sql
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CASE [ expression ] { WHEN boolean_expression THEN then_expression } [ ... ]
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[ ELSE else_expression ]
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END
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```
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### Parameters
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* **boolean_expression**
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Specifies any expression that evaluates to a result type `boolean`. Two or
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more expressions may be combined together using the logical
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operators ( `AND`, `OR` ).
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* **then_expression**
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Specifies the then expression based on the `boolean_expression` condition; `then_expression` and `else_expression` should all be same type or coercible to a common type.
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* **else_expression**
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Specifies the default expression; `then_expression` and `else_expression` should all be same type or coercible to a common type.
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### Examples
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```sql
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CREATE TABLE person (id INT, name STRING, age INT);
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INSERT INTO person VALUES
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(100, 'John', 30),
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(200, 'Mary', NULL),
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(300, 'Mike', 80),
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(400, 'Dan', 50);
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SELECT id, CASE WHEN id > 200 THEN 'bigger' ELSE 'small' END FROM person;
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+------+--------------------------------------------------+
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| id | CASE WHEN (id > 200) THEN bigger ELSE small END |
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+------+--------------------------------------------------+
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| 100 | small |
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| 200 | small |
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| 300 | bigger |
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| 400 | bigger |
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+------+--------------------------------------------------+
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SELECT id, CASE id WHEN 100 then 'bigger' WHEN id > 300 THEN '300' ELSE 'small' END FROM person;
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+------+-----------------------------------------------------------------------------------------------+
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| id | CASE WHEN (id = 100) THEN bigger WHEN (id = CAST((id > 300) AS INT)) THEN 300 ELSE small END |
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+------+-----------------------------------------------------------------------------------------------+
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| 100 | bigger |
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| 200 | small |
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| 300 | small |
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| 400 | small |
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+------+-----------------------------------------------------------------------------------------------+
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SELECT * FROM person
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WHERE
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CASE 1 = 1
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WHEN 100 THEN 'big'
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WHEN 200 THEN 'bigger'
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WHEN 300 THEN 'biggest'
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ELSE 'small'
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END = 'small';
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+------+-------+-------+
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| id | name | age |
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+------+-------+-------+
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| 100 | John | 30 |
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| 200 | Mary | NULL |
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| 300 | Mike | 80 |
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| 400 | Dan | 50 |
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+------+-------+-------+
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```
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### Related Statements
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* [SELECT Main](sql-ref-syntax-qry-select.html)
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* [WHERE Clause](sql-ref-syntax-qry-select-where.html)
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* [GROUP BY Clause](sql-ref-syntax-qry-select-groupby.html)
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* [HAVING Clause](sql-ref-syntax-qry-select-having.html)
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* [ORDER BY Clause](sql-ref-syntax-qry-select-orderby.html)
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* [SORT BY Clause](sql-ref-syntax-qry-select-sortby.html)
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* [DISTRIBUTE BY Clause](sql-ref-syntax-qry-select-distribute-by.html)
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* [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)
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* [PIVOT Clause](sql-ref-syntax-qry-select-pivot.html)
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* [LATERAL VIEW Clause](sql-ref-syntax-qry-select-lateral-view.html)
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