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Merge pull request #42994 from CamiloSierraH/patch-3

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docs/en/engines/table-engines/mergetree-family/aggregatingmergetree.md
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@ -68,36 +68,57 @@ In the results of `SELECT` query, the values of `AggregateFunction` type have im
## Example of an Aggregated Materialized View {#example-of-an-aggregated-materialized-view}
`AggregatingMergeTree` materialized view that watches the `test.visits` table:
We will create the table `test.visits` that contain the raw data:
``` sql
CREATE MATERIALIZED VIEW test.basic
ENGINE = AggregatingMergeTree() PARTITION BY toYYYYMM(StartDate) ORDER BY (CounterID, StartDate)
CREATE TABLE test.visits
(
StartDate DateTime64 NOT NULL,
CounterID UInt64,
Sign Nullable(Int32),
UserID Nullable(Int32)
) ENGINE = MergeTree ORDER BY (StartDate, CounterID);
```
`AggregatingMergeTree` materialized view that watches the `test.visits` table, and use the `AggregateFunction` type:
``` sql
CREATE MATERIALIZED VIEW test.mv_visits
(
StartDate DateTime64 NOT NULL,
CounterID UInt64,
Visits AggregateFunction(sum, Nullable(Int32)),
Users AggregateFunction(uniq, Nullable(Int32))
)
ENGINE = AggregatingMergeTree() ORDER BY (StartDate, CounterID)
AS SELECT
CounterID,
StartDate,
sumState(Sign) AS Visits,
CounterID,
sumState(Sign) AS Visits,
uniqState(UserID) AS Users
FROM test.visits
GROUP BY CounterID, StartDate;
GROUP BY StartDate, CounterID;
```
Inserting data into the `test.visits` table.
``` sql
INSERT INTO test.visits ...
INSERT INTO test.visits (StartDate, CounterID, Sign, UserID)
VALUES (1667446031, 1, 3, 4)
INSERT INTO test.visits (StartDate, CounterID, Sign, UserID)
VALUES (1667446031, 1, 6, 3)
```
The data are inserted in both the table and view `test.basic` that will perform the aggregation.
The data are inserted in both the table and the materialized view `test.mv_visits`.
To get the aggregated data, we need to execute a query such as `SELECT ... GROUP BY ...` from the view `test.basic`:
To get the aggregated data, we need to execute a query such as `SELECT ... GROUP BY ...` from the materialized view `test.mv_visits`:
``` sql
SELECT
StartDate,
sumMerge(Visits) AS Visits,
uniqMerge(Users) AS Users
FROM test.basic
FROM test.mv_visits
GROUP BY StartDate
ORDER BY StartDate;
```