Default catalog

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

CelerData provides an internal catalog to manage the internal data of CelerData. Each CelerData cloud account 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. Log in to your CelerData cloud account.

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, perform the following steps:

1. Use olap_db as the current database.

   USE olap_db;

2. Query data from olap_table.

   SELECT * FROM olap_table limit 1;