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---
toc_priority: 58
toc_title: Permissions for Queries
---
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# Permissions for Queries {#permissions_for_queries}
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Queries in ClickHouse can be divided into several types:
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1. Read data queries: `SELECT` , `SHOW` , `DESCRIBE` , `EXISTS` .
2. Write data queries: `INSERT` , `OPTIMIZE` .
3. Change settings query: `SET` , `USE` .
4. [DDL ](https://en.wikipedia.org/wiki/Data_definition_language ) queries: `CREATE` , `ALTER` , `RENAME` , `ATTACH` , `DETACH` , `DROP` `TRUNCATE` .
5. `KILL QUERY` .
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The following settings regulate user permissions by the type of query:
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- [readonly ](#settings_readonly ) — Restricts permissions for all types of queries except DDL queries.
- [allow\_ddl ](#settings_allow_ddl ) — Restricts permissions for DDL queries.
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`KILL QUERY` can be performed with any settings.
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## readonly {#settings_readonly}
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Restricts permissions for reading data, write data and change settings queries.
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See how the queries are divided into types [above ](#permissions_for_queries ).
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Possible values:
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- 0 — All queries are allowed.
- 1 — Only read data queries are allowed.
- 2 — Read data and change settings queries are allowed.
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After setting `readonly = 1` , the user can’ t change `readonly` and `allow_ddl` settings in the current session.
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When using the `GET` method in the [HTTP interface ](../../interfaces/http.md ), `readonly = 1` is set automatically. To modify data, use the `POST` method.
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Setting `readonly = 1` prohibit the user from changing all the settings. There is a way to prohibit the user
from changing only specific settings, for details see [constraints on settings ](constraints_on_settings.md ).
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Default value: 0
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## allow\_ddl {#settings_allow_ddl}
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Allows or denies [DDL ](https://en.wikipedia.org/wiki/Data_definition_language ) queries.
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See how the queries are divided into types [above ](#permissions_for_queries ).
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Possible values:
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- 0 — DDL queries are not allowed.
- 1 — DDL queries are allowed.
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You can’ t execute `SET allow_ddl = 1` if `allow_ddl = 0` for the current session.
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Default value: 1
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[Original article ](https://clickhouse.tech/docs/en/operations/settings/permissions_for_queries/ ) <!--hide-->