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* Update order-by.md Задокументировал параметры OFFSET и FETCH. * Update prewhere.md Поправляю битые ссылки. * Update prewhere.md Вернул изменения назад. * Update order-by.md Пытаюсь исправить битые ссылки. * Update columns.md Добавил position и compression_codec. * Translation columns.md Сделал перевод на русский язык. * Delete changes order-by.md Удалил изменения в файле order-by. Co-authored-by: Dmitriy <sevirov@yandex-team.ru>
27 lines
2.4 KiB
Markdown
27 lines
2.4 KiB
Markdown
# system.columns {#system-columns}
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Contains information about columns in all the tables.
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You can use this table to get information similar to the [DESCRIBE TABLE](../../sql-reference/statements/misc.md#misc-describe-table) query, but for multiple tables at once.
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The `system.columns` table contains the following columns (the column type is shown in brackets):
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- `database` ([String](../../sql-reference/data-types/string.md)) — Database name.
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- `table` ([String](../../sql-reference/data-types/string.md)) — Table name.
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- `name` ([String](../../sql-reference/data-types/string.md)) — Column name.
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- `type` ([String](../../sql-reference/data-types/string.md)) — Column type.
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- `position` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Ordinal position of a column in a table starting with 1.
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- `default_kind` ([String](../../sql-reference/data-types/string.md)) — Expression type (`DEFAULT`, `MATERIALIZED`, `ALIAS`) for the default value, or an empty string if it is not defined.
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- `default_expression` ([String](../../sql-reference/data-types/string.md)) — Expression for the default value, or an empty string if it is not defined.
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- `data_compressed_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md)) — The size of compressed data, in bytes.
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- `data_uncompressed_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md)) — The size of decompressed data, in bytes.
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- `marks_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md)) — The size of marks, in bytes.
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- `comment` ([String](../../sql-reference/data-types/string.md)) — Comment on the column, or an empty string if it is not defined.
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- `is_in_partition_key` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the column is in the partition expression.
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- `is_in_sorting_key` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the column is in the sorting key expression.
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- `is_in_primary_key` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the column is in the primary key expression.
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- `is_in_sampling_key` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the column is in the sampling key expression.
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- `compression_codec` ([String](../../sql-reference/data-types/string.md)) — Compression codec name.
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[Original article](https://clickhouse.tech/docs/en/operations/system_tables/columns) <!--hide-->
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