In this lesson we will:
- Learn about the information schema which is used as a data dictionary within ClickHouse.
We recommend using a free ClickHouse Cloud Account when studying this lesson
Information Schema
ClickHouse includes a system database called information_schema that is similar in concept to the information schema in other database management systems such as MySQL or PostgreSQL.
The information_schema in ClickHouse contains metadata and system information about the database, tables, and other objects within ClickHouse database.
This information is useful for querying and understanding the structure and status of the database and its tables.
You can query the information_schema tables like any other tables in ClickHouse to retrieve metadata and system information. For example, you can use SQL statements to query the tables and columns tables to understand the structure of your user-created tables.
SELECT *
FROM information_schema.tables
LIMIT 5
Query id: f8c7344c-f115-4e1c-b4f8-22201370203e
┌─table_catalog──────┬─table_schema───────┬─table_name─────────────────────────────────────┬─table_type─┐
│ INFORMATION_SCHEMA │ INFORMATION_SCHEMA │ COLUMNS │ VIEW │
│ INFORMATION_SCHEMA │ INFORMATION_SCHEMA │ SCHEMATA │ VIEW │
│ INFORMATION_SCHEMA │ INFORMATION_SCHEMA │ TABLES │ VIEW │
│ INFORMATION_SCHEMA │ INFORMATION_SCHEMA │ VIEWS │ VIEW │
│ default │ default │ .inner_id.5deb7cb3-19d3-440c-b863-8e0a11d72e5e │ BASE TABLE │
└────────────────────┴────────────────────┴────────────────────────────────────────────────┴────────────┘
5 rows in set. Elapsed: 0.003 sec.