USE Statement

Switches the current session to a specified database. The current database is where any CREATE TABLE, INSERT, SELECT, or other statements act when you specify a table or other object name, without prefixing it with a database name. The new current database applies for the duration of the session or unti another USE statement is executed.

Syntax:

USE db_name

By default, when you connect to an Impala instance, you begin in a database named default.

Usage notes:

Switching the default database is convenient in the following situations:

• To avoid qualifying each reference to a table with the database name. For example, SELECT * FROM t1 JOIN t2 rather than SELECT * FROM db.t1 JOIN db.t2.
• To do a sequence of operations all within the same database, such as creating a table, inserting data, and querying the table.

To start the impala-shell interpreter and automatically issue a USE statement for a particular database, specify the option -d db_name for the impala-shell command. The -d option is useful to run SQL scripts, such as setup or test scripts, against multiple databases without hardcoding a USE statement into the SQL source.

Examples:

See CREATE DATABASE Statement for examples covering CREATE DATABASE, USE, and DROP DATABASE.

Cancellation: Cannot be cancelled.

HDFS permissions: This statement does not touch any HDFS files or directories, therefore no HDFS permissions are required.

Related information:

CREATE DATABASE Statement, DROP DATABASE Statement, SHOW DATABASES