system.columns
Contains information about columns of tables.
DESC system.columns;
+--------------------+---------+------+---------+-------+
| Field | Type | Null | Default | Extra |
+--------------------+---------+------+---------+-------+
| name | VARCHAR | NO | | |
| database | VARCHAR | NO | | |
| table | VARCHAR | NO | | |
| type | VARCHAR | NO | | |
| default_kind | VARCHAR | NO | | |
| default_expression | VARCHAR | NO | | |
| is_nullable | BOOLEAN | NO | false | |
| comment | VARCHAR | NO | | |
SELECT * FROM system.columns WHERE database='system';
+--------------------------+----------+--------------+-------------------+--------------+--------------------+-------------+---------+
| name | database | table | type | default_kind | default_expression | is_nullable | comment |
+--------------------------+----------+--------------+-------------------+--------------+--------------------+-------------+---------+
| dummy | system | one | TINYINT UNSIGNED | | | 0 | |
| name | system | contributors | VARCHAR | | | 0 | |
| id | system | processes | VARCHAR | | | 0 | |
| type | system | processes | VARCHAR | | | 0 | |
| host | system | processes | VARCHAR | | | 1 | |
| user | system | processes | VARCHAR | | | 1 | |
| state | system | processes | VARCHAR | | | 0 | |
| database | system | processes | VARCHAR | | | 0 | |
| extra_info | system | processes | VARCHAR | | | 1 | |
| memory_usage | system | processes | BIGINT | | | 0 | |
| dal_metrics_read_bytes | system | processes | BIGINT UNSIGNED | | | 1 | |
| dal_metrics_write_bytes | system | processes | BIGINT UNSIGNED | | | 1 | |
| scan_progress_read_rows | system | processes | BIGINT UNSIGNED | | | 1 | |
| scan_progress_read_bytes | system | processes | BIGINT UNSIGNED | | | 1 | |
| mysql_connection_id | system | processes | INT UNSIGNED | | | 1 | |
| name | system | credits | VARCHAR | | | 0 | |
| version | system | credits | VARCHAR | | | 0 | |
| license | system | credits | VARCHAR | | | 0 | |
| group | system | configs | VARCHAR | | | 0 | |
| name | system | configs | VARCHAR | | | 0 | |
| value | system | configs | VARCHAR | | | 0 | |
| description | system | configs | VARCHAR | | | 0 | |
| log_type | system | query_log | TINYINT | | | 0 | |
| handler_type | system | query_log | VARCHAR | | | 0 | |
| tenant_id | system | query_log | VARCHAR | | | 0 | |
| cluster_id | system | query_log | VARCHAR | | | 0 | |
| sql_user | system | query_log | VARCHAR | | | 0 | |
| sql_user_quota | system | query_log | VARCHAR | | | 0 | |
| sql_user_privileges | system | query_log | VARCHAR | | | 0 | |
| query_id | system | query_log | VARCHAR | | | 0 | |
| query_kind | system | query_log | VARCHAR | | | 0 | |
| query_text | system | query_log | VARCHAR | | | 0 | |
| event_date | system | query_log | DATE | | | 0 | |
| event_time | system | query_log | TIMESTAMP(3) | | | 0 | |
| current_database | system | query_log | VARCHAR | | | 0 | |
| databases | system | query_log | VARCHAR | | | 0 | |
| tables | system | query_log | VARCHAR | | | 0 | |
| columns | system | query_log | VARCHAR | | | 0 | |
| projections | system | query_log | VARCHAR | | | 0 | |
| written_rows | system | query_log | BIGINT UNSIGNED | | | 0 | |
| written_bytes | system | query_log | BIGINT UNSIGNED | | | 0 | |
| written_io_bytes | system | query_log | BIGINT UNSIGNED | | | 0 | |
| written_io_bytes_cost_ms | system | query_log | BIGINT UNSIGNED | | | 0 | |
| scan_rows | system | query_log | BIGINT UNSIGNED | | | 0 | |
| scan_bytes | system | query_log | BIGINT UNSIGNED | | | 0 | |
| scan_io_bytes | system | query_log | BIGINT UNSIGNED | | | 0 | |
| scan_io_bytes_cost_ms | system | query_log | BIGINT UNSIGNED | | | 0 | |
| scan_partitions | system | query_log | BIGINT UNSIGNED | | | 0 | |
| total_partitions | system | query_log | BIGINT UNSIGNED | | | 0 | |
| result_rows | system | query_log | BIGINT UNSIGNED | | | 0 | |
| result_bytes | system | query_log | BIGINT UNSIGNED | | | 0 | |
| cpu_usage | system | query_log | INT UNSIGNED | | | 0 | |
| memory_usage | system | query_log | BIGINT UNSIGNED | | | 0 | |
| client_info | system | query_log | VARCHAR | | | 0 | |
| client_address | system | query_log | VARCHAR | | | 0 | |
| exception_code | system | query_log | INT | | | 0 | |
| exception_text | system | query_log | VARCHAR | | | 0 | |
| stack_trace | system | query_log | VARCHAR | | | 0 | |
| server_version | system | query_log | VARCHAR | | | 0 | |
| session_settings | system | query_log | VARCHAR | | | 0 | |
| extra | system | query_log | VARCHAR | | | 0 | |
| name | system | columns | VARCHAR | | | 0 | |
| database | system | columns | VARCHAR | | | 0 | |
| table | system | columns | VARCHAR | | | 0 | |
| type | system | columns | VARCHAR | | | 0 | |
| default_kind | system | columns | VARCHAR | | | 0 | |
| default_expression | system | columns | VARCHAR | | | 0 | |
| is_nullable | system | columns | BOOLEAN | | | 0 | |
| comment | system | columns | VARCHAR | | | 0 | |
| Engine | system | engines | VARCHAR | | | 0 | |
| Comment | system | engines | VARCHAR | | | 0 | |
| name | system | databases | VARCHAR | | | 0 | |
| name | system | clusters | VARCHAR | | | 0 | |
| host | system | clusters | VARCHAR | | | 0 | |
| port | system | clusters | SMALLINT UNSIGNED | | | 0 | |
| metric | system | metrics | VARCHAR | | | 0 | |
| kind | system | metrics | VARCHAR | | | 0 | |
| labels | system | metrics | VARCHAR | | | 0 | |
| value | system | metrics | VARCHAR | | | 0 | |
| name | system | settings | VARCHAR | | | 0 | |
| value | system | settings | VARCHAR | | | 0 | |
| default | system | settings | VARCHAR | | | 0 | |
| level | system | settings | VARCHAR | | | 0 | |
| description | system | settings | VARCHAR | | | 0 | |
| type | system | settings | VARCHAR | | | 0 | |
| database | system | tables | VARCHAR | | | 0 | |
| name | system | tables | VARCHAR | | | 0 | |
| engine | system | tables | VARCHAR | | | 0 | |
| created_on | system | tables | VARCHAR | | | 0 | |
| dropped_on | system | tables | VARCHAR | | | 0 | |
| num_rows | system | tables | BIGINT UNSIGNED | | | 1 | |
| data_size | system | tables | BIGINT UNSIGNED | | | 1 | |
| data_compressed_size | system | tables | BIGINT UNSIGNED | | | 1 | |
| index_size | system | tables | BIGINT UNSIGNED | | | 1 | |
| v | system | tracing | BIGINT | | | 0 | |
| name | system | tracing | VARCHAR | | | 0 | |
| msg | system | tracing | VARCHAR | | | 0 | |
| level | system | tracing | TINYINT | | | 0 | |
| hostname | system | tracing | VARCHAR | | | 0 | |
| pid | system | tracing | BIGINT | | | 0 | |
| time | system | tracing | VARCHAR | | | 0 | |
| name | system | functions | VARCHAR | | | 0 | |
| is_builtin | system | functions | BOOLEAN | | | 0 | |
| is_aggregate | system | functions | BOOLEAN | | | 0 | |
| definition | system | functions | VARCHAR | | | 0 | |
| category | system | functions | VARCHAR | | | 0 | |
| description | system | functions | VARCHAR | | | 0 | |
| syntax | system | functions | VARCHAR | | | 0 | |
| example | system | functions | VARCHAR | | | 0 | |
| name | system | users | VARCHAR | | | 0 | |
| hostname | system | users | VARCHAR | | | 0 | |
| auth_type | system | users | VARCHAR | | | 0 | |
| auth_string | system | users | VARCHAR | | | 0 | |
| name | system | roles | VARCHAR | | | 0 | |
| inherited_roles | system | roles | BIGINT UNSIGNED | | | 0 | |
| name | system | stages | VARCHAR | | | 0 | |
| stage_type | system | stages | VARCHAR | | | 0 | |
| stage_params | system | stages | VARCHAR | | | 0 | |
| copy_options | system | stages | VARCHAR | | | 0 | |
| file_format_options | system | stages | VARCHAR | | | 0 | |
| number_of_files | system | stages | BIGINT UNSIGNED | | | 1 | |
| creator | system | stages | VARCHAR | | | 1 | |
| comment | system | stages | VARCHAR | | | 0 | |
+--------------------------+----------+--------------+-------------------+--------------+--------------------+-------------+---------+