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112 lines
5.7 KiB
Markdown
112 lines
5.7 KiB
Markdown
# system.tables {#system-tables}
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Contains metadata of each table that the server knows about.
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[Detached](../../sql-reference/statements/detach.md) tables are not shown in `system.tables`.
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[Temporary tables](../../sql-reference/statements/create/table.md#temporary-tables) are visible in the `system.tables` only in those session where they have been created. They are shown with the empty `database` field and with the `is_temporary` flag switched on.
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Columns:
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- `database` ([String](../../sql-reference/data-types/string.md)) — The name of the database the table is in.
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- `name` ([String](../../sql-reference/data-types/string.md)) — Table name.
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- `engine` ([String](../../sql-reference/data-types/string.md)) — Table engine name (without parameters).
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- `is_temporary` ([UInt8](../../sql-reference/data-types/int-uint.md)) - Flag that indicates whether the table is temporary.
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- `data_path` ([String](../../sql-reference/data-types/string.md)) - Path to the table data in the file system.
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- `metadata_path` ([String](../../sql-reference/data-types/string.md)) - Path to the table metadata in the file system.
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- `metadata_modification_time` ([DateTime](../../sql-reference/data-types/datetime.md)) - Time of latest modification of the table metadata.
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- `dependencies_database` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) - Database dependencies.
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- `dependencies_table` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) - Table dependencies ([MaterializedView](../../engines/table-engines/special/materializedview.md) tables based on the current table).
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- `create_table_query` ([String](../../sql-reference/data-types/string.md)) - The query that was used to create the table.
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- `engine_full` ([String](../../sql-reference/data-types/string.md)) - Parameters of the table engine.
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- `partition_key` ([String](../../sql-reference/data-types/string.md)) - The partition key expression specified in the table.
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- `sorting_key` ([String](../../sql-reference/data-types/string.md)) - The sorting key expression specified in the table.
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- `primary_key` ([String](../../sql-reference/data-types/string.md)) - The primary key expression specified in the table.
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- `sampling_key` ([String](../../sql-reference/data-types/string.md)) - The sampling key expression specified in the table.
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- `storage_policy` ([String](../../sql-reference/data-types/string.md)) - The storage policy:
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- [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md#table_engine-mergetree-multiple-volumes)
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- [Distributed](../../engines/table-engines/special/distributed.md#distributed)
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- `total_rows` ([Nullable](../../sql-reference/data-types/nullable.md)([UInt64](../../sql-reference/data-types/int-uint.md))) - Total number of rows, if it is possible to quickly determine exact number of rows in the table, otherwise `NULL` (including underying `Buffer` table).
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- `total_bytes` ([Nullable](../../sql-reference/data-types/nullable.md)([UInt64](../../sql-reference/data-types/int-uint.md))) - Total number of bytes, if it is possible to quickly determine exact number of bytes for the table on storage, otherwise `NULL` (does not includes any underlying storage).
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- If the table stores data on disk, returns used space on disk (i.e. compressed).
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- If the table stores data in memory, returns approximated number of used bytes in memory.
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- `lifetime_rows` ([Nullable](../../sql-reference/data-types/nullable.md)([UInt64](../../sql-reference/data-types/int-uint.md))) - Total number of rows INSERTed since server start (only for `Buffer` tables).
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- `lifetime_bytes` ([Nullable](../../sql-reference/data-types/nullable.md)([UInt64](../../sql-reference/data-types/int-uint.md))) - Total number of bytes INSERTed since server start (only for `Buffer` tables).
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The `system.tables` table is used in `SHOW TABLES` query implementation.
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**Example**
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```sql
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SELECT * FROM system.tables LIMIT 2 FORMAT Vertical;
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```
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```text
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Row 1:
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──────
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database: system
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name: aggregate_function_combinators
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uuid: 00000000-0000-0000-0000-000000000000
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engine: SystemAggregateFunctionCombinators
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is_temporary: 0
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data_paths: []
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metadata_path: /var/lib/clickhouse/metadata/system/aggregate_function_combinators.sql
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metadata_modification_time: 1970-01-01 03:00:00
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dependencies_database: []
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dependencies_table: []
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create_table_query:
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engine_full:
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partition_key:
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sorting_key:
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primary_key:
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sampling_key:
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storage_policy:
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total_rows: ᴺᵁᴸᴸ
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total_bytes: ᴺᵁᴸᴸ
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Row 2:
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──────
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database: system
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name: asynchronous_metrics
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uuid: 00000000-0000-0000-0000-000000000000
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engine: SystemAsynchronousMetrics
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is_temporary: 0
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data_paths: []
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metadata_path: /var/lib/clickhouse/metadata/system/asynchronous_metrics.sql
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metadata_modification_time: 1970-01-01 03:00:00
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dependencies_database: []
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dependencies_table: []
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create_table_query:
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engine_full:
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partition_key:
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sorting_key:
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primary_key:
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sampling_key:
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storage_policy:
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total_rows: ᴺᵁᴸᴸ
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total_bytes: ᴺᵁᴸᴸ
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```
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[Original article](https://clickhouse.tech/docs/en/operations/system_tables/tables) <!--hide-->
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