ClickHouse/docs/en/sql-reference/statements/alter/delete.md
Dmitriy aca04ebc87 Update files in the 'alter'.
Внес поправки в английскую версию, выполнил перевод на русский язык, подкорректировал некоторые файлы в 'ALTER'.
2020-12-02 23:26:48 +03:00

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---
toc_priority: 39
toc_title: DELETE
---
# ALTER TABLE … DELETE Statement {#alter-mutations}
``` sql
ALTER TABLE [db.]table [ON CLUSTER cluster] DELETE WHERE filter_expr
```
Deletes data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/alter/index.md#mutations).
!!! note "Note"
The `ALTER TABLE` prefix makes this syntax different from most other systems supporting SQL. It is intended to signify that unlike similar queries in OLTP databases this is a heavy operation not designed for frequent use.
The `filter_expr` must be of type `UInt8`. The query deletes rows in the table for which this expression takes a non-zero value.
One query can contain several commands separated by commas.
The synchronicity of the query processing is defined by the [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting. By default, it is asynchronous.
**See also**
- [Mutations](../../../sql-reference/statements/alter/index.md#mutations)
- [Synchronicity of ALTER Queries](../../../sql-reference/statements/alter/index.md#synchronicity-of-alter-queries)
- [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting