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DOCAPI-3911: Aliases for columns in external dictionaries. Some changes in markup (#5638)

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* DOCAPI-3911: Aliases for columns in external dictionaries. Some changes in markup.

* DOCAPI-3911: Fixes.
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BayoNet 2019-06-17 12:08:30 +03:00 committed by Ivan Blinkov
parent 54b1349fb9
commit ee907f2f73
1 changed files with 9 additions and 7 deletions
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docs/en/query_language/dicts/external_dicts_dict_structure.md
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@ -105,12 +105,14 @@ Configuration example:
Configuration fields:
- `name` – The column name.
- `type` – The column type. Sets the method for interpreting data in the source. For example, for MySQL, the field might be `TEXT`, `VARCHAR`, or `BLOB` in the source table, but it can be uploaded as `String`.
- `null_value` – The default value for a non-existing element. In the example, it is an empty string.
- `expression` – The attribute can be an expression. The tag is not required.
- `hierarchical` – Hierarchical support. Mirrored to the parent identifier. By default, ` false`.
- `injective` – Whether the `id -> attribute` image is injective. If ` true`, then you can optimize the ` GROUP BY` clause. By default, `false`.
- `is_object_id` – Whether the query is executed for a MongoDB document by `ObjectID`.
Tag | Description | Required
----|-------------|---------
`name`| Column name. | Yes
`type`| Column type.<br/>Sets the method for interpreting data in the source. For example, for MySQL, the field might be `TEXT`, `VARCHAR`, or `BLOB` in the source table, but it can be uploaded as `String`. | Yes
`null_value` | Default value for a non-existing element.<br/>In the example, it is an empty string. | Yes
`expression` | [Expression](../syntax.md#syntax-expressions) that ClickHouse executes on the value.<br/>The expression can be a column name in the remote SQL database. Thus, you can use it for creating an alias for the remote column.<br/><br/>Default value: no expression. | No
`hierarchical` | Hierarchical support. Mirrored to the parent identifier.<br/><br/>Default value: `false`. | No
`injective` | Flag that shows whether the `id -> attribute` image is injective.<br/>If `true`, then you can optimize the `GROUP BY` clause.<br/><br/>Default value: `false`. | No
`is_object_id` | Flag that shows whether the query is executed for a MongoDB document by `ObjectID`.<br/><br/>Default value: `false`. | No
[Original article](https://clickhouse.yandex/docs/en/query_language/dicts/external_dicts_dict_structure/) <!--hide-->