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198 lines
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198 lines
8.9 KiB
Markdown
---
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id: tutorial-sql-query-view
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title: Get to know Query view
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sidebar_label: Get to know Query view
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---
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This tutorial demonstrates some useful features built into Query view in Apache Druid.
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Query view lets you run [Druid SQL queries](../querying/sql.md) and [native (JSON-based) queries](../querying/querying.md) against ingested data.
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You can use Query view to test and tune queries before you use them in API requests—for example, to perform [SQL-based ingestion](../api-reference/sql-ingestion-api.md). You can also ingest data directly in Query view.
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The tutorial guides you through the steps to ingest sample data and query the ingested data using some Query view features.
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## Prerequisites
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Before you follow the steps in this tutorial, download Druid as described in the [quickstart](./index.md) and have it running on your local machine. You don't need to have loaded any data.
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## Run a demo query to ingest data
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Druid includes demo queries that each demonstrate a different Druid feature—for example transforming data during ingestion and sorting ingested data. Each query has detailed comments to help you learn more.
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In this section you load the demo queries and run a SQL task to ingest sample data into a [table datasource](../querying/datasource.md#table).
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1. Navigate to the Druid console at [http://localhost:8888](http://localhost:8888) and click **Query**.
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2. Click the ellipsis at the bottom of the query window and select **Load demo queries**. Note that loading the demo queries replaces all of your current query tabs. The demo queries load in several tabs:
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3. Click the **Demo 1** tab. This query ingests sample data into a datasource called **kttm_simple**. Click the **Demo 1** tab heading again and note the options—you can rename, copy, and duplicate tabs.
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4. Click **Run** to ingest the data.
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5. When ingestion is complete, Druid displays the time it took to complete the insert query, and the new datasource **kttm_simple** displays in the left pane.
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## View and filter query results
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In this section you run some queries against the new datasource and perform some operations on the query results.
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1. Click **+** to the right of the existing tabs to open a new query tab.
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2. Click the name of the datasource **kttm_simple** in the left pane to display some automatically generated queries:
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3. Click **SELECT * FROM kttm_simple** and run the query.
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4. In the query results pane, click **Chrome** anywhere it appears in the **browser** column then click **Filter on: browser = 'Chrome'** to filter the results.
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## Run aggregate queries
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[Aggregate functions](../querying/sql-aggregations.md) allow you to perform a calculation on a set of values and return a single value.
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In this section you run some queries using aggregate functions and perform some operations on the results, using shortcut features designed to help you build your query.
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1. Open a new query tab.
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2. Click **kttm_simple** in the left pane to display the generated queries.
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3. Click **SELECT COUNT(*) AS "Count" FROM kttm_simple** and run the query.
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4. After you run a query that contains an aggregate function, additional Query view options become available.
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Click the arrow to the left of the **kttm_simple** datasource to display the columns, then click the **country** column. Several options appear to apply country-based filters and aggregate functions to the query:
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5. Click **Aggregate > COUNT(DISTINCT "country")** to add this clause to the query. The query now appears as follows:
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```sql
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SELECT COUNT(*) AS "Count",
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COUNT(DISTINCT "country") AS "dist_country"
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FROM "kttm_simple"
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GROUP BY ()
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```
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Note that you can use column names such as `dist_country` in this example as shortcuts when building your query.
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6. Run the updated query:
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7. Click **Engine: Auto (SQL native)** to display the engine options—**Native** for native (JSON-based) queries, **SQL native** for Druid SQL queries, and **SQL MSQ-task** for SQL-based ingestion.
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Select **Auto** to let Druid select the most efficient engine based on your query input.
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8. From the engine menu you can also edit the query context and turn off some query defaults.
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Deselect **Use approximate COUNT(DISTINCT)** and rerun the query. The country count in the results decreases because the computation has become more exact. See [SQL aggregation functions](../querying/sql-aggregations.md) for more information.
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9. Query view can provide information about a function, in case you aren't sure exactly what it does.
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Delete the contents of the query line `COUNT(DISTINCT country) AS dist_country` and type `COUNT(DISTINCT)` to replace it. A help dialog for the function displays:
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Click outside the help window to close it.
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10. You can perform actions on calculated columns in the results pane.
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Click the results column heading **dist_country COUNT(DISTINCT "country")** to see the available options:
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11. Select **Edit column** and change the **Output name** to **Distinct countries**.
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## Generate an explain plan
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In this section you generate an explain plan for a query. An explain plan shows the full query details and all of the operations Druid performs to execute it.
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Druid optimizes queries of certain [types](../querying/sql-translation.md#query-types)—see [SQL query translation](../querying/sql-translation.md) for information on how to interpret an explain plan and use the details to improve query performance.
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1. Open a new query tab.
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2. Click **kttm_simple** in the left pane to display the generated queries.
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3. Click **SELECT * FROM kttm_simple** and run the query.
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4. Click the ellipsis at the bottom of the query window and select **Explain SQL query**. The query plan opens in a new window:
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5. Click **Open in new tab**. You can review the query details and modify it as required.
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6. Change the limit from 1001 to 2001:
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```sql
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"Limit": 2001,
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```
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and run the query to confirm that the updated query returns 2,001 results.
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## Try out a few more features
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In this section you try out a few more useful Query view features.
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### Use calculator mode
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Queries without a FROM clause run in calculator mode—this can be useful to help you understand how functions work. See the [Druid SQL functions](../querying/sql-functions.md) reference for more information.
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1. Open a new query tab and enter the following:
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```sql
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SELECT SQRT(49)
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```
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2. Run the query to produce the result `7`.
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### Download query results
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You can download query results in CSV, TSV, or newline-delimited JSON format.
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1. Open a new query tab and run a query, for example:
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```sql
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SELECT DISTINCT platform
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FROM kttm_simple
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```
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2. Above the results pane, click the down arrow and select **Download results as… CSV**.
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### View query history
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In any query tab, click the ellipsis at the bottom of the query window and select **Query history**.
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You can click the links on the left to view queries run at a particular date and time, and open a previously run query in a new query tab.
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## Further reading
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For more information on ingestion and querying data, see the following topics:
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- [Quickstart](./index.md) for information on getting started with Druid.
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- [Tutorial: Querying data](tutorial-query.md) for example queries to run on Druid data.
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- [Ingestion](../ingestion/index.md) for an overview of ingestion and the ingestion methods available in Druid.
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- [SQL-based ingestion](../multi-stage-query/index.md) for an overview of SQL-based ingestion.
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- [SQL-based ingestion query examples](../multi-stage-query/examples.md) for examples of SQL-based ingestion for various use cases.
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- [Introduction to Druid SQL](https://github.com/implydata/learn-druid/tree/main/notebooks) to learn more about Druid SQL.
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