mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-09-28 12:40:49 +00:00
28 lines
1.5 KiB
Markdown
28 lines
1.5 KiB
Markdown
|
---
|
||
|
|
machine_translated: true
|
||
|
|
machine_translated_rev: 5decc73b5dc60054f19087d3690c4eb99446a6c3
|
||
|
|
---
|
||
|
|
|
||
|
|
# 系统。列 {#system-columns}
|
||
|
|
|
||
|
|
包含有关所有表中列的信息。
|
||
|
|
|
||
|
|
您可以使用此表获取类似于以下内容的信息 [DESCRIBE TABLE](../../sql-reference/statements/misc.md#misc-describe-table) 查询，但对于多个表一次。
|
||
|
|
|
||
|
|
该 `system.columns` 表包含以下列（列类型显示在括号中):
|
||
|
|
|
||
|
|
- `database` (String) — Database name.
|
||
|
|
- `table` (String) — Table name.
|
||
|
|
- `name` (String) — Column name.
|
||
|
|
- `type` (String) — Column type.
|
||
|
|
- `default_kind` (String) — Expression type (`DEFAULT`, `MATERIALIZED`, `ALIAS`)为默认值，如果没有定义，则为空字符串。
|
||
|
|
- `default_expression` (String) — Expression for the default value, or an empty string if it is not defined.
|
||
|
|
- `data_compressed_bytes` (UInt64) — The size of compressed data, in bytes.
|
||
|
|
- `data_uncompressed_bytes` (UInt64) — The size of decompressed data, in bytes.
|
||
|
|
- `marks_bytes` (UInt64) — The size of marks, in bytes.
|
||
|
|
- `comment` (String) — Comment on the column, or an empty string if it is not defined.
|
||
|
|
- `is_in_partition_key` (UInt8) — Flag that indicates whether the column is in the partition expression.
|
||
|
|
- `is_in_sorting_key` (UInt8) — Flag that indicates whether the column is in the sorting key expression.
|
||
|
|
- `is_in_primary_key` (UInt8) — Flag that indicates whether the column is in the primary key expression.
|
||
|
|
- `is_in_sampling_key` (UInt8) — Flag that indicates whether the column is in the sampling key expression.
|