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126 lines
6.6 KiB
Markdown
126 lines
6.6 KiB
Markdown
# 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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- `as_select` ([String](../../sql-reference/data-types/string.md)) - `SELECT` query for view.
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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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- `comment` ([String](../../sql-reference/data-types/string.md)) - The comment for the table.
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- `has_own_data` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the table itself stores some data on disk or only accesses some other source.
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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: base
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name: t1
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uuid: 81b1c20a-b7c6-4116-a2ce-7583fb6b6736
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engine: MergeTree
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is_temporary: 0
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data_paths: ['/var/lib/clickhouse/store/81b/81b1c20a-b7c6-4116-a2ce-7583fb6b6736/']
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metadata_path: /var/lib/clickhouse/store/461/461cf698-fd0b-406d-8c01-5d8fd5748a91/t1.sql
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metadata_modification_time: 2021-01-25 19:14:32
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dependencies_database: []
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dependencies_table: []
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create_table_query: CREATE TABLE base.t1 (`n` UInt64) ENGINE = MergeTree ORDER BY n SETTINGS index_granularity = 8192
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engine_full: MergeTree ORDER BY n SETTINGS index_granularity = 8192
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as_select: SELECT database AS table_catalog
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partition_key:
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sorting_key: n
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primary_key: n
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sampling_key:
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storage_policy: default
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total_rows: 1
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total_bytes: 99
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lifetime_rows: ᴺᵁᴸᴸ
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lifetime_bytes: ᴺᵁᴸᴸ
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comment:
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has_own_data: 0
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Row 2:
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──────
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database: default
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name: 53r93yleapyears
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uuid: 00000000-0000-0000-0000-000000000000
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engine: MergeTree
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is_temporary: 0
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data_paths: ['/var/lib/clickhouse/data/default/53r93yleapyears/']
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metadata_path: /var/lib/clickhouse/metadata/default/53r93yleapyears.sql
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metadata_modification_time: 2020-09-23 09:05:36
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dependencies_database: []
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dependencies_table: []
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create_table_query: CREATE TABLE default.`53r93yleapyears` (`id` Int8, `febdays` Int8) ENGINE = MergeTree ORDER BY id SETTINGS index_granularity = 8192
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engine_full: MergeTree ORDER BY id SETTINGS index_granularity = 8192
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as_select: SELECT name AS catalog_name
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partition_key:
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sorting_key: id
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primary_key: id
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sampling_key:
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storage_policy: default
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total_rows: 2
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total_bytes: 155
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lifetime_rows: ᴺᵁᴸᴸ
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lifetime_bytes: ᴺᵁᴸᴸ
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comment:
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has_own_data: 0
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```
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