luoyuxia commented on code in PR #20696: URL: https://github.com/apache/flink/pull/20696#discussion_r964572857
########## docs/content.zh/docs/dev/table/hiveCompatibility/hiveDialect/Queries/sub-queries.md: ########## @@ -0,0 +1,69 @@ +--- +title: "Sub-Queries" +weight: 8 +type: docs +--- +<!-- +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. +--> + +# Sub-Queries + +## Sub-Queries in the FROM Clause + +### Description + +Hive dialect supports sub-queries in the `FROM` clause. The sub-query has to be given a name because every table in a `FROM` clause must have a name. +Columns in the sub-query select list must have unique names. +The columns in the sub-query select list are available in the outer query just like columns of a table. +The sub-query can also be a query expression with `UNION`. Hive dialect supports arbitrary levels of sub-queries. + +### Syntax + +```sql +select_statement from ( subquery_select_statement ) [ AS ] name Review Comment: Maybe we can rename `subquery_select_statement` to `select_statement ` since `subquery_select_statement` is actually also select statment. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
