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23 lines
716 B
Markdown
23 lines
716 B
Markdown
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---
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toc_priority: 43
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toc_title: CONSTRAINT
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---
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# Manipulating Constraints {#manipulations-with-constraints}
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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 ADD CONSTRAINT constraint_name CHECK expression;
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ALTER TABLE [db].name DROP CONSTRAINT constraint_name;
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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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!!! warning "Warning"
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Constraint check **will not be executed** on existing data if it was added.
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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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