Introduction to logical views

This document provides an overview of BigQuery support for logical views.

Overview

A view is a virtual table defined by a SQL query. The default type of view for BigQuery is a logical view. Query results contain only the data from the tables and fields specified in the query that defines the view.

The query that defines a view is run each time the view is queried.

Types of views

Although logical views are the default type of view, if you frequently query a large or computationally expensive view, then you should consider creating a materialized view, which is a precomputed view that periodically caches the results of a query for increased performance and efficiency.

However, you can often improve performance of a logical view without the need to create a materialized view by querying only a subset of your data, or by using other techniques.

You can also create an authorized view to share a subset of data from a source dataset to a view in a secondary dataset. You can then share this view to specific users and groups (principals) who can view the data you share and run queries on it, but who can't access the source dataset directly.

You can create an authorized view for either a logical or materialized view. An authorized view for a materialized view is called an authorized materialized view.

Use cases

Common use cases for views include the following:

  • Provide an easily reusable name for a complex query or a limited set of data that you can then authorize other users to access. After you create a view, a user can then query the view as they would a table.
  • Abstract and store calculation and join logic in a common object to simplify query use.
  • Provide access to a subset of data and calculation logic without providing access to the base tables.
  • Optimize queries with high computation cost and small dataset results for several use cases.

You can also use views in other contexts:

Comparison to materialized views

Logical views are virtual and provide a reusable reference to a set of data, but don't physically store any data. Materialized views are defined using SQL, like a logical view, but physically store the data which BigQuery uses to improve performance. For further comparison, see materialized views features.

Logical views limitations

BigQuery views are subject to the following limitations:

  • Views are read-only. For example, you can't run queries that insert, update, or delete data.
  • The dataset that contains your view and the dataset that contains the tables referenced by the view must be in the same location.
  • A reference inside of a view must be qualified with a dataset. The default dataset doesn't affect a view body.
  • You cannot use the TableDataList JSON API method to retrieve data from a view. For more information, see Tabledata: list.
  • You cannot mix GoogleSQL and legacy SQL queries when using views. A GoogleSQL query cannot reference a view defined using legacy SQL syntax.
  • You cannot reference query parameters in views.
  • The schemas of the underlying tables are stored with the view when the view is created. If columns are added, deleted, or modified after the view is created, the view isn't automatically updated and the reported schema will remain inaccurate until the view SQL definition is changed or the view is recreated. Even though the reported schema may be inaccurate, all submitted queries produce accurate results.
  • You cannot automatically update a legacy SQL view to GoogleSQL syntax. To modify the query used to define a view, you can use the following:
  • You cannot include a temporary user-defined function or a temporary table in the SQL query that defines a view.
  • You cannot reference a view in a wildcard table query.

Logical views quotas

For information on quotas and limits that apply to views, see View limits.

SQL queries used to define views are also subject to the quotas on query jobs.

Logical views pricing

BigQuery uses logical views by default, not materialized views. Because views are not materialized by default, the query that defines the view is run each time the view is queried. Queries are billed according to the total amount of data in all table fields referenced directly or indirectly by the top-level query.

Logical views security

To control access to views in BigQuery, see Authorized views.

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