mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-16 03:12:43 +00:00
25 lines
798 B
Markdown
25 lines
798 B
Markdown
---
|
|
slug: /en/sql-reference/statements/alter/constraint
|
|
sidebar_position: 43
|
|
sidebar_label: CONSTRAINT
|
|
---
|
|
|
|
# Manipulating Constraints
|
|
|
|
Constraints could be added or deleted using following syntax:
|
|
|
|
``` sql
|
|
ALTER TABLE [db].name [ON CLUSTER cluster] ADD CONSTRAINT [IF NOT EXISTS] constraint_name CHECK expression;
|
|
ALTER TABLE [db].name [ON CLUSTER cluster] DROP CONSTRAINT [IF EXISTS] constraint_name;
|
|
```
|
|
|
|
See more on [constraints](../../../sql-reference/statements/create/table.md#constraints).
|
|
|
|
Queries will add or remove metadata about constraints from table, so they are processed immediately.
|
|
|
|
:::tip
|
|
Constraint check **will not be executed** on existing data if it was added.
|
|
:::
|
|
|
|
All changes on replicated tables are broadcasted to ZooKeeper and will be applied on other replicas as well.
|