System tables ​

System relations expose server metadata, effective settings and request observations. Always use the system qualifier to distinguish them from user tables.

Read and manage ​

Live metadata and observation relations are read-only. databases, tables and settings also support validated management writes after a database is selected. Ordinary table changes should use CREATE, ALTER and DROP; use the documented setting interface for each name.

Some catalogs, such as databases, formats and functions, can be read before USE. A standalone embedded connection does not provide these service relations.

Inventory ​

system.system_tables is a read-only view with schema_name and table_name columns. SHOW SYSTEM TABLES presents the same service inventory.

Relations ​

• system.columns
• system.databases
• system.formats
• system.functions
• system.processes
• system.query_log
• system.settings
• system.tables