system.columns
Contains information about columns of tables.
mysql> select * from columns;
+---------------------+----------+--------------+---------------+-------------+
| name | database | table | data_type | is_nullable |
+---------------------+----------+--------------+---------------+-------------+
| name | system | configs | String | 0 |
| value | system | configs | String | 0 |
| group | system | configs | String | 0 |
| description | system | configs | String | 0 |
| name | system | clusters | String | 0 |
| host | system | clusters | String | 0 |
| port | system | clusters | UInt16 | 0 |
| database | system | tables | String | 0 |
| name | system | tables | String | 0 |
| engine | system | tables | String | 0 |
| created_on | system | tables | String | 0 |
| id | system | processes | String | 0 |
| type | system | processes | String | 0 |
| host | system | processes | String | 1 |
| user | system | processes | String | 1 |
| state | system | processes | String | 0 |
| database | system | processes | String | 0 |
| extra_info | system | processes | String | 1 |
| memory_usage | system | processes | Int64 | 1 |
| v | system | tracing | Int64 | 0 |
| name | system | tracing | String | 0 |
| msg | system | tracing | String | 0 |
| level | system | tracing | Int8 | 0 |
| hostname | system | tracing | String | 0 |
| pid | system | tracing | Int64 | 0 |
| time | system | tracing | String | 0 |
| name | system | credits | String | 0 |
| version | system | credits | String | 0 |
| license | system | credits | String | 0 |
| name | system | databases | String | 0 |
| log_type | system | query_log | Int8 | 0 |
| handler_type | system | query_log | String | 0 |
| tenant_id | system | query_log | String | 0 |
| cluster_id | system | query_log | String | 0 |
| sql_user | system | query_log | String | 0 |
| sql_user_quota | system | query_log | String | 0 |
| sql_user_privileges | system | query_log | String | 0 |
| query_id | system | query_log | String | 0 |
| query_kind | system | query_log | String | 0 |
| query_text | system | query_log | String | 0 |
| event_date | system | query_log | Date32 | 0 |
| event_time | system | query_log | DateTime64(3) | 0 |
| current_database | system | query_log | String | 0 |
| databases | system | query_log | String | 0 |
| tables | system | query_log | String | 0 |
| columns | system | query_log | String | 0 |
| projections | system | query_log | String | 0 |
| written_rows | system | query_log | UInt64 | 0 |
| written_bytes | system | query_log | UInt64 | 0 |
| read_rows | system | query_log | UInt64 | 0 |
| read_bytes | system | query_log | UInt64 | 0 |
| result_rows | system | query_log | UInt64 | 0 |
| result_bytes | system | query_log | UInt64 | 0 |
| cpu_usage | system | query_log | UInt32 | 0 |
| memory_usage | system | query_log | UInt64 | 0 |
| client_info | system | query_log | String | 0 |
| client_address | system | query_log | String | 0 |
| exception_code | system | query_log | Int32 | 0 |
| exception_text | system | query_log | String | 0 |
| stack_trace | system | query_log | String | 0 |
| server_version | system | query_log | String | 0 |
| extra | system | query_log | String | 0 |
| name | system | functions | String | 0 |
| is_aggregate | system | functions | Boolean | 0 |
| name | system | columns | String | 0 |
| database | system | columns | String | 0 |
| table | system | columns | String | 0 |
| data_type | system | columns | String | 0 |
| is_nullable | system | columns | Boolean | 0 |
| name | system | settings | String | 0 |
| value | system | settings | String | 0 |
| default_value | system | settings | String | 0 |
| description | system | settings | String | 0 |
| name | system | contributors | String | 0 |
| name | system | users | String | 0 |
| hostname | system | users | String | 0 |
| password | system | users | String | 1 |
| password_type | system | users | UInt8 | 0 |
| metric | system | metrics | String | 0 |
| kind | system | metrics | String | 0 |
| labels | system | metrics | String | 0 |
| value | system | metrics | String | 0 |
| dummy | system | one | UInt8 | 0 |
| a | default | t1 | Int32 | 1 |
+---------------------+----------+--------------+---------------+-------------+