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clafiry DISTINCT is optional for COUNT() (#15394)

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Charles Smith 2023-11-28 03:22:16 -08:00 committed by GitHub
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docs/querying/sql-aggregations.md
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@ -70,7 +70,7 @@ In the aggregation functions supported by Druid, only `COUNT`, `ARRAY_AGG`, and
|Function|Notes|Default|
|--------|-----|-------|
|`COUNT(*)`|Counts the number of rows.|`0`|
|`COUNT(DISTINCT expr)`|Counts distinct values of `expr`.<br /><br />When `useApproximateCountDistinct` is set to "true" (the default), this is an alias for `APPROX_COUNT_DISTINCT`. The specific algorithm depends on the value of [`druid.sql.approxCountDistinct.function`](../configuration/index.md#sql). In this mode, you can use strings, numbers, or prebuilt sketches. If counting prebuilt sketches, the prebuilt sketch type must match the selected algorithm.<br /><br />When `useApproximateCountDistinct` is set to "false", the computation will be exact. In this case, `expr` must be string or numeric, since exact counts are not possible using prebuilt sketches. In exact mode, only one distinct count per query is permitted unless `useGroupingSetForExactDistinct` is enabled.<br /><br />Counts each distinct value in a [`multi-value`](../querying/multi-value-dimensions.md)-row separately.|`0`|
|`COUNT([DISTINCT] expr)`|Counts the values of `expr`.<br /><br />By default, using DISTINCT serves as an alias for `APPROX_COUNT_DISTINCT` (`useApproximateCountDistinct=true`). The specific algorithm depends on the value of [`druid.sql.approxCountDistinct.function`](../configuration/index.md#sql). In this mode, you can use strings, numbers, or prebuilt sketches. If counting prebuilt sketches, the prebuilt sketch type must match the selected algorithm.<br /><br />When `useApproximateCountDistinct=false`, returns the exact computation. In this case, `expr` must be string or numeric, since exact counts are not possible using prebuilt sketches. In exact mode, only one distinct count per query is permitted unless `useGroupingSetForExactDistinct` is enabled.<br /><br />Counts each distinct value in a [`multi-value`](../querying/multi-value-dimensions.md)-row separately.|`0`|
|`SUM(expr)`|Sums numbers.|`null` or `0` if `druid.generic.useDefaultValueForNull=true` (legacy mode)|
|`MIN(expr)`|Takes the minimum of numbers.|`null` or `9223372036854775807` (maximum LONG value) if `druid.generic.useDefaultValueForNull=true` (legacy mode)|
|`MAX(expr)`|Takes the maximum of numbers.|`null` or `-9223372036854775808` (minimum LONG value) if `druid.generic.useDefaultValueForNull=true` (legacy mode)|