Examples of using a cross-database query

Use the following examples to help learn how to set up a cross-database query that references an Amazon Redshift database.

To start, create databases db1 and db2 and users user1 and user2 in your Amazon Redshift cluster. For more information, see CREATE DATABASE and CREATE USER.

--As user1 on db1
CREATE DATABASE db1;

CREATE DATABASE db2;

CREATE USER user1 PASSWORD 'Redshift01';

CREATE USER user2 PASSWORD 'Redshift01';

As user1 on db1, create a table, grant access privileges to user2, and insert values into table1. For more information, see GRANT and INSERT.

--As user1 on db1
CREATE TABLE table1 (c1 int, c2 int, c3 int);

GRANT SELECT ON table1 TO user2;

INSERT INTO table1 VALUES (1,2,3),(4,5,6),(7,8,9);

As user2 on db2, run a cross-database query in db2 using the three-part notation.

--As user2 on db2
SELECT * from db1.public.table1 ORDER BY c1;
c1 | c2  | c3
---+-----+----
1  |  2  | 3
4  |  5  | 6
7  |  8  | 9
(3 rows)

As user2 on db2, create an external schema and run a cross-database query in db2 using the external schema notation.

--As user2 on db2
CREATE EXTERNAL SCHEMA db1_public_sch
FROM REDSHIFT DATABASE 'db1' SCHEMA 'public';

SELECT * FROM db1_public_sch.table1 ORDER BY c1;

c1  | c2 | c3
----+----+----
1   | 2  | 3
4   | 5  | 6
7   | 8  | 9
(3 rows)

To create different views and grant permissions to those views, as user1 on db1, do the following.

--As user1 on db1
CREATE VIEW regular_view AS SELECT c1 FROM table1;

GRANT SELECT ON regular_view TO user2;


CREATE MATERIALIZED VIEW mat_view AS SELECT c2 FROM table1;

GRANT SELECT ON mat_view TO user2;


CREATE VIEW late_bind_view AS SELECT c3 FROM public.table1 WITH NO SCHEMA BINDING;

GRANT SELECT ON late_bind_view TO user2;

As user2 on db2, run the following cross-database query using the three-part notation to view the particular view.

--As user2 on db2
SELECT * FROM db1.public.regular_view;
c1
----
1
4
7
(3 rows)

SELECT * FROM db1.public.mat_view;
c2
----
8
5
2
(3 rows)

SELECT * FROM db1.public.late_bind_view;
c3
----
3
6 
9
(3 rows)

As user2 on db2, run the following cross-database query using the external schema notation to query the late-binding view.

--As user2 on db2
SELECT * FROM db1_public_sch.late_bind_view;
c3
----
3
6
9
(3 rows)

As user2 on db2, run the following command using connected tables in a single query.

--As user2 on db2
CREATE TABLE table1 (a int, b int, c int);

INSERT INTO table1 VALUES (1,2,3), (4,5,6), (7,8,9);

SELECT a AS col_1, (db1.public.table1.c2 + b) AS sum_col2, (db1.public.table1.c3 + c) AS sum_col3 FROM db1.public.table1, table1 WHERE db1.public.table1.c1 = a;
col_1 | sum_col2 | sum_col3
------+----------+----------
1     | 4        | 6
4     | 10       | 12
7     | 16       | 18
(3 rows)

The following example lists all databases on the cluster.

select database_name, database_owner, database_type 
from svv_redshift_databases 
where database_name in ('db1', 'db2');

 database_name | database_owner | database_type 
---------------+----------------+---------------
 db1           |            100 | local
 db2           |            100 | local
(2 rows)

The following example lists all Amazon Redshift schemas of all databases on the cluster.

select database_name, schema_name, schema_owner, schema_type 
from svv_redshift_schemas 
where database_name in ('db1', 'db2');

 database_name |    schema_name     | schema_owner | schema_type 
---------------+--------------------+--------------+-------------
 db1           | pg_catalog         |            1 | local
 db1           | public             |            1 | local
 db1           | information_schema |            1 | local
 db2           | pg_catalog         |            1 | local
 db2           | public             |            1 | local
 db2           | information_schema |            1 | local
(6 rows)

The following example lists all Amazon Redshift tables or views of all databases on the cluster.

select database_name, schema_name, table_name, table_type 
from svv_redshift_tables 
where database_name in ('db1', 'db2') and schema_name in ('public');

 database_name | schema_name |     table_name      | table_type 
---------------+-------------+---------------------+------------
 db1           | public      | late_bind_view      | VIEW
 db1           | public      | mat_view            | VIEW
 db1           | public      | mv_tbl__mat_view__0 | TABLE
 db1           | public      | regular_view        | VIEW
 db1           | public      | table1              | TABLE
 db2           | public      | table2              | TABLE
(6 rows)

The following example lists all Amazon Redshift and external schemas of all databases on the cluster.

select database_name, schema_name, schema_owner, schema_type 
from svv_all_schemas where database_name in ('db1', 'db2') ;

 database_name |    schema_name     | schema_owner | schema_type 
---------------+--------------------+--------------+-------------
 db1           | pg_catalog         |            1 | local
 db1           | public             |            1 | local
 db1           | information_schema |            1 | local
 db2           | pg_catalog         |            1 | local
 db2           | public             |            1 | local
 db2           | information_schema |            1 | local
 db2           | db1_public_sch     |            1 | external
(7 rows)

The following example lists all Amazon Redshift and external tables of all databases on the cluster.

select database_name, schema_name, table_name, table_type 
from svv_all_tables 
where database_name in ('db1', 'db2') and schema_name in ('public');

 database_name | schema_name |     table_name      | table_type 
---------------+-------------+---------------------+------------
 db1           | public      | regular_view        | VIEW
 db1           | public      | mv_tbl__mat_view__0 | TABLE
 db1           | public      | mat_view            | VIEW
 db1           | public      | late_bind_view      | VIEW
 db1           | public      | table1              | TABLE
 db2           | public      | table2              | TABLE
(6 rows)