runningConcurrency() english description changed.

docs/en/sql-reference/functions/other-functions.md

@@ -911,29 +911,30 @@ Same as for [runningDifference](../../sql-reference/functions/other-functions.md
 
 ## runningConcurrency {#runningconcurrency}
 
-Given a series of beginning time and ending time of events, this function calculates concurrency of the events at each of the data point, that is, the beginning time.
-
-!!! warning "Warning"
-    Events spanning multiple data blocks will not be processed correctly. The function resets its state for each new data block.
-
-The result of the function depends on the order of data in the block. It assumes the beginning time is sorted in ascending order.
+Calculates the number of events that are concurrent at event start time.
 
 **Syntax**
 
 ``` sql
-runningConcurrency(begin, end)
+runningConcurrency(start, end)
 ```
 
+An event has start time and end time. Columns with these times must have the same data type. The start time is included in an event, while the stop time is excluded. The function analyses each event start time and calculates the total number of events that are active including the starting event.
+
+!!! warning "Warning"
+    Every data block is processed separately. If events from different data blocks overlap then they can not be processed correctly.
+
+!!! warning "Warning"
+    Events must be ordered by the start time in ascending order. If this requirement is not held the function raises an exception.
+
 **Arguments**
 
--   `begin` — A column for the beginning time of events (inclusive). [Date](../../sql-reference/data-types/date.md), [DateTime](../../sql-reference/data-types/datetime.md), or [DateTime64](../../sql-reference/data-types/datetime64.md).
--   `end` — A column for the ending time of events (exclusive).  [Date](../../sql-reference/data-types/date.md), [DateTime](../../sql-reference/data-types/datetime.md), or [DateTime64](../../sql-reference/data-types/datetime64.md).
-
-Note that two columns `begin` and `end` must have the same type.
+-   `start` — A column with start time of events. [Date](../../sql-reference/data-types/date.md), [DateTime](../../sql-reference/data-types/datetime.md), or [DateTime64](../../sql-reference/data-types/datetime64.md).
+-   `end` — A column with end time of events.  [Date](../../sql-reference/data-types/date.md), [DateTime](../../sql-reference/data-types/datetime.md), or [DateTime64](../../sql-reference/data-types/datetime64.md).
 
 **Returned values**
 
--   The concurrency of events at the data point.
+-   The number of concurrent events at each event start time.
 
 Type: [UInt32](../../sql-reference/data-types/int-uint.md)
 
@@ -942,31 +943,29 @@ Type: [UInt32](../../sql-reference/data-types/int-uint.md)
 Input table:
 
 ``` text
-┌───────────────begin─┬─────────────────end─┐
-│ 2020-12-01 00:00:00 │ 2020-12-01 00:59:59 │
-│ 2020-12-01 00:30:00 │ 2020-12-01 00:59:59 │
-│ 2020-12-01 00:40:00 │ 2020-12-01 01:30:30 │
-│ 2020-12-01 01:10:00 │ 2020-12-01 01:30:30 │
-│ 2020-12-01 01:50:00 │ 2020-12-01 01:59:59 │
-└─────────────────────┴─────────────────────┘
+┌──────start─┬────────end─┐
+│ 2021-03-03 │ 2021-03-11 │
+│ 2021-03-06 │ 2021-03-12 │
+│ 2021-03-07 │ 2021-03-08 │
+│ 2021-03-11 │ 2021-03-12 │
+└────────────┴────────────┘
 ```
 
 Query:
 
 ``` sql
-SELECT runningConcurrency(begin, end) FROM example
+SELECT start, runningConcurrency(start, end) FROM example_table;
 ```
 
 Result:
 
 ``` text
-┌─runningConcurrency(begin, end)─┐
-│                              1 │
-│                              2 │
-│                              3 │
-│                              2 │
-│                              1 │
-└────────────────────────────────┘
+┌──────start─┬─runningConcurrency(start, end)─┐
+│ 2021-03-03 │                              1 │
+│ 2021-03-06 │                              2 │
+│ 2021-03-07 │                              3 │
+│ 2021-03-11 │                              2 │
+└────────────┴────────────────────────────────┘
 ```
 
 ## MACNumToString(num) {#macnumtostringnum}