DROP DATABASE statement
DROP DATABASE statement removes a database from the system. The
physical operations involve removing the metadata for the database from the metastore, and
deleting the corresponding
*.db directory from HDFS.
DROP (DATABASE|SCHEMA) [IF EXISTS] database_name [RESTRICT | CASCADE];
Statement type: DDL
By default, the database must be empty before it can be dropped, to avoid losing any data.
In Impala 2.3 and higher, you can include the
CASCADE clause to
make Impala drop all tables and other objects in the database before dropping the database
RESTRICT clause enforces the original requirement that the
database be empty before being dropped. Because the
RESTRICT behavior is
still the default, this clause is optional.
The automatic dropping resulting from the
CASCADE clause follows the same rules as the
DROP VIEW, and
DROP FUNCTION statements.
In particular, the HDFS directories and data files for any external tables are left behind when the
tables are removed.
When you do not use the
CASCADE clause, drop or move all the objects inside the database manually
before dropping the database itself:
SHOW TABLESstatement to locate all tables and views in the database, and issue
DROP VIEWstatements to remove them all.
SHOW AGGREGATE FUNCTIONSstatements to locate all user-defined functions in the database, and issue
DROP AGGREGATE FUNCTIONstatements to remove them all.
To keep tables or views contained by a database while removing the database itself, use
ALTER VIEWto move the relevant objects to a different database before dropping the original database.
You cannot drop the current database, that is, the database your session connected to
either through the
USE statement or the
-d option of impala-shell.
USE statement to switch to a different database first.
default database is always available, issuing
USE default is a convenient way to leave the current database
before dropping it.
When you drop a database in Impala, the database can no longer be used by Hive.
See CREATE DATABASE statement for examples covering
Amazon S3 considerations:
In Impala 2.6 and higher, Impala DDL
statements such as
DROP DATABASE CASCADE,
DROP TABLE, and
TABLE [ADD|DROP] PARTITION can create or remove folders as needed in the Amazon
S3 system. Prior to Impala 2.6, you had to create folders yourself and point Impala
database, tables, or partitions at them, and manually remove folders when no longer needed.
Cancellation: Cannot be cancelled.
The user ID that the impalad daemon runs under,
impala user, must have write
permission for the directory associated with the database.
create database first_db; use first_db; create table t1 (x int); create database second_db; use second_db; -- Each database has its own namespace for tables. -- You can reuse the same table names in each database. create table t1 (s string); create database temp; -- You can either USE a database after creating it, -- or qualify all references to the table name with the name of the database. -- Here, tables T2 and T3 are both created in the TEMP database. create table temp.t2 (x int, y int); use database temp; create table t3 (s string); -- You cannot drop a database while it is selected by the USE statement. drop database temp; ERROR: AnalysisException: Cannot drop current default database: temp -- The always-available database 'default' is a convenient one to USE -- before dropping a database you created. use default; -- Before dropping a database, first drop all the tables inside it, -- or in Impala 2.3 and higher use the CASCADE clause. drop database temp; ERROR: ImpalaRuntimeException: Error making 'dropDatabase' RPC to Hive Metastore: CAUSED BY: InvalidOperationException: Database temp is not empty show tables in temp; +------+ | name | +------+ | t3 | +------+ -- Impala 2.3 and higher: drop database temp cascade; -- Earlier releases: drop table temp.t3; drop database temp;