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18 lines
874 B
Markdown
18 lines
874 B
Markdown
---
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sidebar_position: 41
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sidebar_label: ORDER BY
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---
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# 操作排序键表达式 {#manipulations-with-key-expressions}
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```sql
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ALTER TABLE [db].name [ON CLUSTER cluster] MODIFY ORDER BY new_expression
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```
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该命令将表的[排序键](../../../engines/table-engines/mergetree-family/mergetree.md)更改为 `new_expression`(表达式或表达式元组)。主键保持不变。
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从某种意义上说，该命令是轻量级的，它只更改元数据。要保持数据部分行按排序键表达式排序的属性，您不能向排序键添加包含现有列的表达式(仅在相同的`ALTER`查询中由`ADD COLUMN`命令添加的列，没有默认的列值)。
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!!! note "备注"
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它只适用于[`MergeTree`](../../../engines/table-engines/mergetree-family/mergetree.md)表族(包括[replicated](../../../engines/table-engines/mergetree-family/replication.md)表)。
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