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28 lines
1.5 KiB
Markdown
28 lines
1.5 KiB
Markdown
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machine_translated: true
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machine_translated_rev: 5decc73b5dc60054f19087d3690c4eb99446a6c3
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---
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# 系统。列 {#system-columns}
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包含有关所有表中列的信息。
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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。
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该 `system.columns` 表包含以下列（列类型显示在括号中):
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- `database` (String) — Database name.
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- `table` (String) — Table name.
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- `name` (String) — Column name.
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- `type` (String) — Column type.
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- `default_kind` (String) — Expression type (`DEFAULT`, `MATERIALIZED`, `ALIAS`)为默认值，如果没有定义，则为空字符串。
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- `default_expression` (String) — Expression for the default value, or an empty string if it is not defined.
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- `data_compressed_bytes` (UInt64) — The size of compressed data, in bytes.
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- `data_uncompressed_bytes` (UInt64) — The size of decompressed data, in bytes.
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- `marks_bytes` (UInt64) — The size of marks, in bytes.
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- `comment` (String) — Comment on the column, or an empty string if it is not defined.
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- `is_in_partition_key` (UInt8) — Flag that indicates whether the column is in the partition expression.
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- `is_in_sorting_key` (UInt8) — Flag that indicates whether the column is in the sorting key expression.
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- `is_in_primary_key` (UInt8) — Flag that indicates whether the column is in the primary key expression.
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- `is_in_sampling_key` (UInt8) — Flag that indicates whether the column is in the sampling key expression.
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