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64 lines
1.6 KiB
Markdown
64 lines
1.6 KiB
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/maxintersections
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sidebar_position: 360
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title: maxIntersections
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---
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# maxIntersections
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Aggregate function that calculates the maximum number of times that a group of intervals intersects each other (if all the intervals intersect at least once).
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The syntax is:
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```sql
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maxIntersections(start_column, end_column)
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```
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**Arguments**
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- `start_column` – the numeric column that represents the start of each interval. If `start_column` is `NULL` or 0 then the interval will be skipped.
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- `end_column` - the numeric column that represents the end of each interval. If `end_column` is `NULL` or 0 then the interval will be skipped.
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**Returned value**
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Returns the maximum number of intersected intervals.
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**Example**
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```sql
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CREATE TABLE my_events (
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start UInt32,
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end UInt32
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)
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Engine = MergeTree
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ORDER BY tuple();
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INSERT INTO my_events VALUES
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(1, 3),
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(1, 6),
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(2, 5),
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(3, 7);
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```
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The intervals look like the following:
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```response
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1 - 3
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1 - - - - 6
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2 - - 5
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3 - - - 7
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```
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Three of these intervals have a common value (the value is `4`, but the value that is common is not important, we are measuring the count of the intersections). The intervals `(1,3)` and `(3,7)` share an endpoint but are not considered intersecting by the `maxIntersections` function.
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```sql
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SELECT maxIntersections(start, end) FROM my_events;
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```
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Response:
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```response
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3
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```
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If you have multiple occurrences of the maximum interval, you can use the [`maxIntersectionsPosition` function](./maxintersectionsposition.md) to locate the number and location of those occurrences. |