--- title: Combine and reuse ES|QL queries description: ES|QL provides several ways to combine, filter, and reuse query results beyond querying a single index. Choose the mechanism that best fits your goal... url: https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-combine-reuse-queries products: - Elasticsearch applies_to: - Elastic Cloud Serverless: Generally available - Elastic Stack: Generally available --- # Combine and reuse ES|QL queries ES|QL provides several ways to combine, filter, and reuse query results beyond querying a single index. Choose the mechanism that best fits your goal. | Mechanism | What it does | When to use | |----------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------| | [Subquery](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-subquery) | Nests a query inside another query, either to [combine result sets](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-from-subquery) or to [filter rows](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-in-subquery) | You need to use the results of one query inside another | | [View](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-views) | Saves a named query as a virtual index that any `FROM` can reference | You want to define a query once and reuse it across multiple requests | | [`FORK`](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/commands/fork) | Sends the same incoming rows through multiple independent branches | You want to run different processing on the same data in one query | ## Comparing views, subqueries, and FORK [Views](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-views), [`FROM` subqueries](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-from-subquery), [`IN` subqueries](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-in-subquery), and [`FORK`](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/commands/fork) share several traits but differ in important ways. `IN` subqueries operate differently from the other three. They filter rows rather than producing branches, so the similarities and differences below apply to `FROM` subqueries, views, and `FORK` only. ### Similarities - **Dynamic execution.** All three run at query time, so results reflect the current state of the data. - **Union of columns.** Columns from multiple branches are merged into a single table. Missing columns are filled with `null` values. - **Supported commands.** Complex processing commands can be used inside both views and `FROM` subqueries, as detailed in the [description of `FROM` subqueries](/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-from-subquery#description). - **No nested branching.** Nested branching is generally not supported, but views can work around this through [query compaction](/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-views#query-compaction). - **Maximum branch count.** All three share the same maximum branch count of 8. ### How FORK differs - `FORK` does not include a source command. Every branch receives the same incoming rows and columns. - `FROM` subqueries and views each have their own source command (`FROM`, `TS`, or `ROW`), so branches can read from different sources with different columns. - Only one `FORK` command is allowed per query, so nested branches are not possible. `FROM` subqueries and views have similar restrictions, but views can partially work around them through query compaction. ### How views differ from FROM subqueries - Views must be defined using the [REST API](/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-views#create-and-manage-views) before they can be used in queries. Subqueries are written inline and require no setup. - Views have names that are unique within the index namespace. A view cannot share a name with an index. - Views can be nested (up to a depth of 10), with two restrictions: - Cyclic references are not allowed. For example, if `viewA` references `viewB` and `viewB` references `viewC`, then `viewC` cannot reference `viewA`. Cycles are detected at query time. - No more than one branching point can exist across the nesting chain. - `FROM` subqueries do not support further `FROM` subqueries or `FORK` inside them, but can contain `IN` subqueries. Views allow nested branching under [limited conditions](/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-views#nesting-and-branching). ## Related alternatives Depending on your goal, one of these alternatives may be a better fit: - [`LOOKUP JOIN`](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-lookup-join): enrich rows by joining against a lookup index on a key field. - [`ENRICH`](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-enrich-data): augment rows with data from an enrich policy. - [Query multiple indices](https://www.elastic.co/elastic/docs-builder/docs/3802/reference/query-languages/esql/esql-multi-index): use comma-separated index patterns or wildcards in a single `FROM` to query across indices without subqueries.