ClickHouse/docs/en/engines/table-engines/index.md

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---
toc_folder_title: Table Engines
toc_priority: 26
toc_title: Introduction
---
# Table Engines {#table_engines}
The table engine (type of table) determines:
- How and where data is stored, where to write it to, and where to read it from.
- Which queries are supported, and how.
- Concurrent data access.
- Use of indexes, if present.
- Whether multithreaded request execution is possible.
- Data replication parameters.
## Engine Families {#engine-families}
### MergeTree {#mergetree}
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The most universal and functional table engines for high-load tasks. The property shared by these engines is quick data insertion with subsequent background data processing. `MergeTree` family engines support data replication (with [Replicated\*](../../engines/table-engines/mergetree-family/replication.md#table_engines-replication) versions of engines), partitioning, secondary data-skipping indexes, and other features not supported in other engines.
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Engines in the family:
- [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md#mergetree)
- [ReplacingMergeTree](../../engines/table-engines/mergetree-family/replacingmergetree.md#replacingmergetree)
- [SummingMergeTree](../../engines/table-engines/mergetree-family/summingmergetree.md#summingmergetree)
- [AggregatingMergeTree](../../engines/table-engines/mergetree-family/aggregatingmergetree.md#aggregatingmergetree)
- [CollapsingMergeTree](../../engines/table-engines/mergetree-family/collapsingmergetree.md#table_engine-collapsingmergetree)
- [VersionedCollapsingMergeTree](../../engines/table-engines/mergetree-family/versionedcollapsingmergetree.md#versionedcollapsingmergetree)
- [GraphiteMergeTree](../../engines/table-engines/mergetree-family/graphitemergetree.md#graphitemergetree)
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### Log {#log}
Lightweight [engines](../../engines/table-engines/log-family/index.md) with minimum functionality. Theyre the most effective when you need to quickly write many small tables (up to approximately 1 million rows) and read them later as a whole.
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Engines in the family:
- [TinyLog](../../engines/table-engines/log-family/tinylog.md#tinylog)
- [StripeLog](../../engines/table-engines/log-family/stripelog.md#stripelog)
- [Log](../../engines/table-engines/log-family/log.md#log)
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### Integration Engines {#integration-engines}
Engines for communicating with other data storage and processing systems.
Engines in the family:
- [Kafka](../../engines/table-engines/integrations/kafka.md#kafka)
- [MySQL](../../engines/table-engines/integrations/mysql.md#mysql)
- [ODBC](../../engines/table-engines/integrations/odbc.md#table-engine-odbc)
- [JDBC](../../engines/table-engines/integrations/jdbc.md#table-engine-jdbc)
- [HDFS](../../engines/table-engines/integrations/hdfs.md#hdfs)
- [S3](../../engines/table-engines/integrations/s3.md#table_engines-s3)
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### Special Engines {#special-engines}
Engines in the family:
- [Distributed](../../engines/table-engines/special/distributed.md#distributed)
- [MaterializedView](../../engines/table-engines/special/materializedview.md#materializedview)
- [Dictionary](../../engines/table-engines/special/dictionary.md#dictionary)
- [Merge](../../engines/table-engines/special/merge.md#merge)
- [File](../../engines/table-engines/special/file.md#file)
- [Null](../../engines/table-engines/special/null.md#null)
- [Set](../../engines/table-engines/special/set.md#set)
- [Join](../../engines/table-engines/special/join.md#join)
- [URL](../../engines/table-engines/special/url.md#table_engines-url)
- [View](../../engines/table-engines/special/view.md#table_engines-view)
- [Memory](../../engines/table-engines/special/memory.md#memory)
- [Buffer](../../engines/table-engines/special/buffer.md#buffer)
DOCS-624: Fixing links to nowhere (#10675) * enbaskakova-DOCSUP-652 (#101) * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" * Update docs/en/sql_reference/aggregate_functions/combinators.md Co-Authored-By: BayoNet <da-daos@yandex.ru> * Update docs/en/sql_reference/aggregate_functions/combinators.md Co-Authored-By: BayoNet <da-daos@yandex.ru> * Update docs/en/sql_reference/aggregate_functions/combinators.md Co-Authored-By: BayoNet <da-daos@yandex.ru> * Update docs/en/sql_reference/aggregate_functions/combinators.md Co-Authored-By: BayoNet <da-daos@yandex.ru> * Update docs/en/sql_reference/aggregate_functions/combinators.md Co-Authored-By: BayoNet <da-daos@yandex.ru> * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" * "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited" Co-authored-by: elenbaskakova <elenbaskakova@yandex-team.ru> Co-authored-by: BayoNet <da-daos@yandex.ru> * Revert "enbaskakova-DOCSUP-652 (#101)" (#107) This reverts commit 639fee7610f28e421d14e535b7def3f466e7efca. * CLICKHOUSEDOCS-624: Fixed links. Was 60, became 13. * CLICKHOUSEDOCS-624: Finished fix links in Enlish version. * CLICKHOUSEDOCS-624: Fixed RU links Co-authored-by: elenaspb2019 <47083263+elenaspb2019@users.noreply.github.com> Co-authored-by: elenbaskakova <elenbaskakova@yandex-team.ru> Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru>
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## Virtual Columns {#table_engines-virtual_columns}
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Virtual column is an integral table engine attribute that is defined in the engine source code.
You shouldnt specify virtual columns in the `CREATE TABLE` query and you cant see them in `SHOW CREATE TABLE` and `DESCRIBE TABLE` query results. Virtual columns are also read-only, so you cant insert data into virtual columns.
To select data from a virtual column, you must specify its name in the `SELECT` query. `SELECT *` doesnt return values from virtual columns.
If you create a table with a column that has the same name as one of the table virtual columns, the virtual column becomes inaccessible. We dont recommend doing this. To help avoid conflicts, virtual column names are usually prefixed with an underscore.
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[Original article](https://clickhouse.tech/docs/en/engines/table-engines/) <!--hide-->