mirror of https://github.com/apache/druid.git
160 lines
3.4 KiB
Markdown
160 lines
3.4 KiB
Markdown
---
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layout: doc_page
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---
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# Filter groupBy Query Results
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A having clause is a JSON object identifying which rows from a groupBy query should be returned, by specifying conditions on aggregated values.
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It is essentially the equivalent of the HAVING clause in SQL.
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Druid supports the following types of having clauses.
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### Query filters
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Query filter HavingSpecs allow all [Druid query filters](filters.html) to be used in the Having part of the query.
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The grammar for a query filter HavingSpec is:
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```json
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{
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"type" : "filter",
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"filter" : <any Druid query filter>
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}
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```
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For example, to use a selector filter:
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```json
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{
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"type" : "filter",
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"filter" : {
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"type": "selector",
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"dimension" : "<dimension>",
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"value" : "<dimension_value>"
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}
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}
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```
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Note that behavior of the "filter" HavingSpec on an output field named "\_\_time" differs from most other HavingSpecs.
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Unlike most other HavingSpecs, it will act on each row's timestamp rather than an output field named "\_\_time". We
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recommend avoiding naming output fields "\_\_time". Future versions of Druid may enforce this.
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### Numeric filters
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The simplest having clause is a numeric filter.
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Numeric filters can be used as the base filters for more complex boolean expressions of filters.
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Here's an example of a having-clause numeric filter:
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```json
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{
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"type": "greaterThan",
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"aggregation": "myAggMetric",
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"value": 100
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}
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```
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#### Equal To
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The equalTo filter will match rows with a specific aggregate value.
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The grammar for an `equalTo` filter is as follows:
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```json
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{
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"type": "equalTo",
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"aggregation": "<aggregate_metric>",
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"value": <numeric_value>
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}
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```
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This is the equivalent of `HAVING <aggregate> = <value>`.
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#### Greater Than
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The greaterThan filter will match rows with aggregate values greater than the given value.
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The grammar for a `greaterThan` filter is as follows:
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```json
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{
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"type": "greaterThan",
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"aggregation": "<aggregate_metric>",
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"value": <numeric_value>
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}
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```
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This is the equivalent of `HAVING <aggregate> > <value>`.
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#### Less Than
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The lessThan filter will match rows with aggregate values less than the specified value.
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The grammar for a `greaterThan` filter is as follows:
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```json
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{
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"type": "lessThan",
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"aggregation": "<aggregate_metric>",
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"value": <numeric_value>
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}
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```
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This is the equivalent of `HAVING <aggregate> < <value>`.
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### Dimension Selector Filter
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#### dimSelector
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The dimSelector filter will match rows with dimension values equal to the specified value.
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The grammar for a `dimSelector` filter is as follows:
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```json
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{
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"type": "dimSelector",
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"dimension": "<dimension>",
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"value": <dimension_value>
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}
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```
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### Logical expression filters
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#### AND
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The grammar for an AND filter is as follows:
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```json
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{
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"type": "and",
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"havingSpecs": [<having clause>, <having clause>, ...]
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}
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```
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The having clauses in `havingSpecs` can be any other having clause defined on this page.
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#### OR
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The grammar for an OR filter is as follows:
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```json
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{
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"type": "or",
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"havingSpecs": [<having clause>, <having clause>, ...]
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}
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```
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The having clauses in `havingSpecs` can be any other having clause defined on this page.
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#### NOT
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The grammar for a NOT filter is as follows:
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```json
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{
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"type": "not",
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"havingSpec": <having clause>
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}
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```
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The having clause specified at `havingSpec` can be any other having clause defined on this page.
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