2020-07-14 21:02:41 +00:00
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---
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2022-08-28 14:53:34 +00:00
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slug: /en/sql-reference/statements/alter/constraint
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2022-04-09 13:29:05 +00:00
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sidebar_position: 43
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sidebar_label: CONSTRAINT
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2020-07-14 21:02:41 +00:00
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---
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2022-06-02 10:55:18 +00:00
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# Manipulating Constraints
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2020-07-14 21:02:41 +00:00
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Constraints could be added or deleted using following syntax:
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``` sql
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ALTER TABLE [db].name [ON CLUSTER cluster] ADD CONSTRAINT constraint_name CHECK expression;
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ALTER TABLE [db].name [ON CLUSTER cluster] DROP CONSTRAINT constraint_name;
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2020-07-14 21:02:41 +00:00
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```
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See more on [constraints](../../../sql-reference/statements/create/table.md#constraints).
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Queries will add or remove metadata about constraints from table so they are processed immediately.
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2023-03-27 18:54:05 +00:00
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:::tip
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Constraint check **will not be executed** on existing data if it was added.
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:::
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All changes on replicated tables are broadcasted to ZooKeeper and will be applied on other replicas as well.
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