wuchong commented on a change in pull request #16997: URL: https://github.com/apache/flink/pull/16997#discussion_r698434348
########## File path: docs/content.zh/docs/dev/table/sql/queries/window-join.md ########## @@ -0,0 +1,192 @@ +--- +title: "窗口关联" +weight: 10 +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. +--> + +# Window Join +{{< label Streaming >}} + +A window join adds the dimension of time into the join criteria themselves. In doing so, the window join joins the elements of two streams that share a common key and lie in the same window. The semantic of window join is same to the [DataStream window join]({{< ref "docs/dev/datastream/operators/joining" >}}#window-join) + +For streaming queries, unlike other joins on continuous tables, window join does not emit intermediate results but only emits final results at the end of the window. Moreover, window join purge all intermediate state when no longer needed. + +Usually, Window Join is used with [Windowing TVF]({{< ref "docs/dev/table/sql/queries/window-tvf" >}}). Besides, Window Join could follow after other operations based on [Windowing TVF]({{< ref "docs/dev/table/sql/queries/window-tvf" >}}), such as [Window Aggregation]({{< ref "docs/dev/table/sql/queries/window-agg" >}}), [Window TopN]({{< ref "docs/dev/table/sql/queries/window-topn">}}) and [Window Join]({{< ref "docs/dev/table/sql/queries/window-join">}}). + +Currently, Window Join requires the join on condition contains window starts equality of input tables and window ends equality of input tables. + +Window Join supports INNER/LEFT/RIGHT/FULL OUTER/ANTI/SEMI JOIN. + +## INNER/LEFT/RIGHT/FULL OUTER + +The following shows the syntax of the INNER/LEFT/RIGHT/FULL OUTER Window Join statement. + +```sql +SELECT ... +FROM L [LEFT|RIGHT|FULL OUTER] JOIN R -- L and R are relations applied windowing TVF +ON L.window_start = R.window_start AND L.window_end = R.window_end AND ... +``` + +The syntax of INNER/LEFT/RIGHT/FULL OUTER WINDOW JOIN are very similar with each other, we only give an example for FULL OUTER JOIN here. +When performing a window join, all elements with a common key and a common tumbling window are joined together. We only give an example for a Window Join which works on a Tumble Window TVF. +By scoping the region of time for the join into fixed five-minute intervals, we chopped our datasets into two distinct windows of time: [12:00, 12:05) and [12:05, 12:10). The L2 and R2 rows could not join together because they fell into separate windows. + +```sql +Flink SQL> desc LeftTable; ++-------------+------------------------+------+-----+--------+---------------------------------+ +| name | type | null | key | extras | watermark | ++-------------+------------------------+------+-----+--------+---------------------------------+ +| row_time | TIMESTAMP(3) *ROWTIME* | true | | | `Time` - INTERVAL '1' SECOND | Review comment: ```suggestion | row_time | TIMESTAMP(3) *ROWTIME* | true | | | rowtime - INTERVAL '1' SECOND | ``` ########## File path: docs/content.zh/docs/dev/table/sql/queries/window-join.md ########## @@ -0,0 +1,192 @@ +--- +title: "窗口关联" +weight: 10 +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. +--> + +# Window Join +{{< label Streaming >}} + +A window join adds the dimension of time into the join criteria themselves. In doing so, the window join joins the elements of two streams that share a common key and lie in the same window. The semantic of window join is same to the [DataStream window join]({{< ref "docs/dev/datastream/operators/joining" >}}#window-join) + +For streaming queries, unlike other joins on continuous tables, window join does not emit intermediate results but only emits final results at the end of the window. Moreover, window join purge all intermediate state when no longer needed. + +Usually, Window Join is used with [Windowing TVF]({{< ref "docs/dev/table/sql/queries/window-tvf" >}}). Besides, Window Join could follow after other operations based on [Windowing TVF]({{< ref "docs/dev/table/sql/queries/window-tvf" >}}), such as [Window Aggregation]({{< ref "docs/dev/table/sql/queries/window-agg" >}}), [Window TopN]({{< ref "docs/dev/table/sql/queries/window-topn">}}) and [Window Join]({{< ref "docs/dev/table/sql/queries/window-join">}}). + +Currently, Window Join requires the join on condition contains window starts equality of input tables and window ends equality of input tables. + +Window Join supports INNER/LEFT/RIGHT/FULL OUTER/ANTI/SEMI JOIN. + +## INNER/LEFT/RIGHT/FULL OUTER + +The following shows the syntax of the INNER/LEFT/RIGHT/FULL OUTER Window Join statement. + +```sql +SELECT ... +FROM L [LEFT|RIGHT|FULL OUTER] JOIN R -- L and R are relations applied windowing TVF +ON L.window_start = R.window_start AND L.window_end = R.window_end AND ... +``` + +The syntax of INNER/LEFT/RIGHT/FULL OUTER WINDOW JOIN are very similar with each other, we only give an example for FULL OUTER JOIN here. +When performing a window join, all elements with a common key and a common tumbling window are joined together. We only give an example for a Window Join which works on a Tumble Window TVF. +By scoping the region of time for the join into fixed five-minute intervals, we chopped our datasets into two distinct windows of time: [12:00, 12:05) and [12:05, 12:10). The L2 and R2 rows could not join together because they fell into separate windows. + +```sql +Flink SQL> desc LeftTable; ++-------------+------------------------+------+-----+--------+---------------------------------+ +| name | type | null | key | extras | watermark | ++-------------+------------------------+------+-----+--------+---------------------------------+ +| row_time | TIMESTAMP(3) *ROWTIME* | true | | | `Time` - INTERVAL '1' SECOND | +| num | INT | true | | | | +| id | STRING | true | | | | ++-------------+------------------------+------+-----+--------+---------------------------------+ + +Flink SQL> SELECT * FROM LeftTable; ++------------------+-------+------+ +| row_time | num | id | ++------------------+-------+------+ +| 2020-04-15 12:02 | 1 | L1 | +| 2020-04-15 12:06 | 2 | L2 | +| 2020-04-15 12:03 | 3 | L3 | ++------------------+-------+------+ + +Flink SQL> desc RightTable; ++-------------+------------------------+------+-----+--------+---------------------------------+ +| name | type | null | key | extras | watermark | ++-------------+------------------------+------+-----+--------+---------------------------------+ +| row_time | TIMESTAMP(3) *ROWTIME* | true | | | `Time` - INTERVAL '1' SECOND | Review comment: ```suggestion | row_time | TIMESTAMP(3) *ROWTIME* | true | | | row_time - INTERVAL '1' SECOND | ``` -- 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: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
