mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-17 05:03:20 +00:00
126 lines
6.6 KiB
Markdown
126 lines
6.6 KiB
Markdown
# system.tables {#system-tables}
|
||
|
||
Contains metadata of each table that the server knows about.
|
||
|
||
[Detached](../../sql-reference/statements/detach.md) tables are not shown in `system.tables`.
|
||
|
||
[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.
|
||
|
||
Columns:
|
||
|
||
- `database` ([String](../../sql-reference/data-types/string.md)) — The name of the database the table is in.
|
||
|
||
- `name` ([String](../../sql-reference/data-types/string.md)) — Table name.
|
||
|
||
- `engine` ([String](../../sql-reference/data-types/string.md)) — Table engine name (without parameters).
|
||
|
||
- `is_temporary` ([UInt8](../../sql-reference/data-types/int-uint.md)) - Flag that indicates whether the table is temporary.
|
||
|
||
- `data_path` ([String](../../sql-reference/data-types/string.md)) - Path to the table data in the file system.
|
||
|
||
- `metadata_path` ([String](../../sql-reference/data-types/string.md)) - Path to the table metadata in the file system.
|
||
|
||
- `metadata_modification_time` ([DateTime](../../sql-reference/data-types/datetime.md)) - Time of latest modification of the table metadata.
|
||
|
||
- `dependencies_database` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) - Database dependencies.
|
||
|
||
- `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).
|
||
|
||
- `create_table_query` ([String](../../sql-reference/data-types/string.md)) - The query that was used to create the table.
|
||
|
||
- `engine_full` ([String](../../sql-reference/data-types/string.md)) - Parameters of the table engine.
|
||
|
||
- `as_select` ([String](../../sql-reference/data-types/string.md)) - `SELECT` query for view.
|
||
|
||
- `partition_key` ([String](../../sql-reference/data-types/string.md)) - The partition key expression specified in the table.
|
||
|
||
- `sorting_key` ([String](../../sql-reference/data-types/string.md)) - The sorting key expression specified in the table.
|
||
|
||
- `primary_key` ([String](../../sql-reference/data-types/string.md)) - The primary key expression specified in the table.
|
||
|
||
- `sampling_key` ([String](../../sql-reference/data-types/string.md)) - The sampling key expression specified in the table.
|
||
|
||
- `storage_policy` ([String](../../sql-reference/data-types/string.md)) - The storage policy:
|
||
|
||
- [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md#table_engine-mergetree-multiple-volumes)
|
||
- [Distributed](../../engines/table-engines/special/distributed.md#distributed)
|
||
|
||
- `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).
|
||
|
||
- `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).
|
||
|
||
- If the table stores data on disk, returns used space on disk (i.e. compressed).
|
||
- If the table stores data in memory, returns approximated number of used bytes in memory.
|
||
|
||
- `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).
|
||
|
||
- `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).
|
||
|
||
- `comment` ([String](../../sql-reference/data-types/string.md)) - The comment for the table.
|
||
|
||
- `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.
|
||
|
||
The `system.tables` table is used in `SHOW TABLES` query implementation.
|
||
|
||
**Example**
|
||
|
||
```sql
|
||
SELECT * FROM system.tables LIMIT 2 FORMAT Vertical;
|
||
```
|
||
|
||
```text
|
||
Row 1:
|
||
──────
|
||
database: base
|
||
name: t1
|
||
uuid: 81b1c20a-b7c6-4116-a2ce-7583fb6b6736
|
||
engine: MergeTree
|
||
is_temporary: 0
|
||
data_paths: ['/var/lib/clickhouse/store/81b/81b1c20a-b7c6-4116-a2ce-7583fb6b6736/']
|
||
metadata_path: /var/lib/clickhouse/store/461/461cf698-fd0b-406d-8c01-5d8fd5748a91/t1.sql
|
||
metadata_modification_time: 2021-01-25 19:14:32
|
||
dependencies_database: []
|
||
dependencies_table: []
|
||
create_table_query: CREATE TABLE base.t1 (`n` UInt64) ENGINE = MergeTree ORDER BY n SETTINGS index_granularity = 8192
|
||
engine_full: MergeTree ORDER BY n SETTINGS index_granularity = 8192
|
||
as_select: SELECT database AS table_catalog
|
||
partition_key:
|
||
sorting_key: n
|
||
primary_key: n
|
||
sampling_key:
|
||
storage_policy: default
|
||
total_rows: 1
|
||
total_bytes: 99
|
||
lifetime_rows: ᴺᵁᴸᴸ
|
||
lifetime_bytes: ᴺᵁᴸᴸ
|
||
comment:
|
||
has_own_data: 0
|
||
|
||
Row 2:
|
||
──────
|
||
database: default
|
||
name: 53r93yleapyears
|
||
uuid: 00000000-0000-0000-0000-000000000000
|
||
engine: MergeTree
|
||
is_temporary: 0
|
||
data_paths: ['/var/lib/clickhouse/data/default/53r93yleapyears/']
|
||
metadata_path: /var/lib/clickhouse/metadata/default/53r93yleapyears.sql
|
||
metadata_modification_time: 2020-09-23 09:05:36
|
||
dependencies_database: []
|
||
dependencies_table: []
|
||
create_table_query: CREATE TABLE default.`53r93yleapyears` (`id` Int8, `febdays` Int8) ENGINE = MergeTree ORDER BY id SETTINGS index_granularity = 8192
|
||
engine_full: MergeTree ORDER BY id SETTINGS index_granularity = 8192
|
||
as_select: SELECT name AS catalog_name
|
||
partition_key:
|
||
sorting_key: id
|
||
primary_key: id
|
||
sampling_key:
|
||
storage_policy: default
|
||
total_rows: 2
|
||
total_bytes: 155
|
||
lifetime_rows: ᴺᵁᴸᴸ
|
||
lifetime_bytes: ᴺᵁᴸᴸ
|
||
comment:
|
||
has_own_data: 0
|
||
```
|