Default catalog

This topic describes what the default catalog is, and how to query the internal data of StarRocks by using the default catalog.

StarRocks 2.3 and later provide an internal catalog to manage the internal data of StarRocks. Each StarRocks cluster has only one internal catalog named default_catalog. Currently, you cannot modify the name of the internal catalog or create a new internal catalog.

Query internal data

1. Connect your StarRocks cluster.

   • If you use the MySQL client to connect the StarRocks cluster, you go to default_catalog by default after connecting.
   • If you use JDBC to connect the StarRocks cluster, you can go directly to the destination database in the default catalog by specifying default_catalog.db_name when connecting.

2. (Optional) Use SHOW DATABASES to view databases:

   SHOW DATABASES;

   Or

   SHOW DATABASES FROM <catalog_name>;

3. (Optional) Use SET CATALOG to switch to the destination catalog in the current session:

   SET CATALOG <catalog_name>;

   Then, use USE to specify the active database in the current session:

   USE <db_name>;

   Or, you can use USE to directly go to the active database in the destination catalog:

   USE <catalog_name>.<db_name>;

4. Use SELECT to query internal data:

   SELECT * FROM <table_name>;

   If you do not specify the active database in the preceding steps, you can directly specify it in a select query:

   SELECT * FROM <db_name>.<table_name>;

   Or

   SELECT * FROM default_catalog.<db_name>.<table_name>;

Examples

To query data in olap_db.olap_table, you can perform one of the following operations:

USE olap_db;
SELECT * FROM olap_table limit 1;

Or

SELECT * FROM olap_db.olap_table limit 1;     

Or

SELECT * FROM default_catalog.olap_db.olap_table limit 1;      

References

To query data from external data sources, see Query external data.