ClickHouse/docs/en/engines/table-engines/special/set.md

---
toc_priority: 39
toc_title: Set
---

# Set Table Engine {#set}

A data set that is always in RAM. It is intended for use on the right side of the `IN` operator (see the section “IN operators”).

You can use `INSERT` to insert data in the table. New elements will be added to the data set, while duplicates will be ignored.
But you can’t perform `SELECT` from the table. The only way to retrieve data is by using it in the right half of the `IN` operator.

Data is always located in RAM. For `INSERT`, the blocks of inserted data are also written to the directory of tables on the disk. When starting the server, this data is loaded to RAM. In other words, after restarting, the data remains in place.

For a rough server restart, the block of data on the disk might be lost or damaged. In the latter case, you may need to manually delete the file with damaged data.

[Original article](https://clickhouse.tech/docs/en/operations/table_engines/set/) <!--hide-->
-												Get rid of toc_en.yml (#10023)


											
										
										
											2020-04-03 13:23:32 +00:00
+								---
 								toc_priority: 39
 								toc_title: Set
 								---
-												Update set.md
											
										
										
											2020-06-10 20:14:51 +00:00
+								# Set Table Engine {#set}
-												Initial commit if EN docs

											
										
										
											2017-04-03 19:49:50 +00:00
-												Update set.md
											
										
										
											2020-06-10 20:14:51 +00:00
+								A data set that is always in RAM. It is intended for use on the right side of the `IN` operator (see the section “IN operators”).
-												Initial commit if EN docs

											
										
										
											2017-04-03 19:49:50 +00:00
-												Update set.md
											
										
										
											2020-06-10 20:14:51 +00:00
+								You can use `INSERT` to insert data in the table. New elements will be added to the data set, while duplicates will be ignored.
 								But you can’t perform `SELECT` from the table. The only way to retrieve data is by using it in the right half of the `IN` operator.
-												Initial commit if EN docs

											
										
										
											2017-04-03 19:49:50 +00:00
-												Update set.md
											
										
										
											2020-06-10 20:14:51 +00:00
+								Data is always located in RAM. For `INSERT`, the blocks of inserted data are also written to the directory of tables on the disk. When starting the server, this data is loaded to RAM. In other words, after restarting, the data remains in place.
-												Initial commit if EN docs

											
										
										
											2017-04-03 19:49:50 +00:00
-												Table engines

											
										
										
											2017-04-26 17:26:17 +00:00
+								For a rough server restart, the block of data on the disk might be lost or damaged. In the latter case, you may need to manually delete the file with damaged data.
-												Sources for english documentation switched to Markdown.
Edit page link is fixed too for both language versions of documentation.

											
										
										
											2017-12-28 15:13:23 +00:00
-												Domain change in docs

											
										
										
											2020-01-30 10:34:55 +00:00
+								[Original article](https://clickhouse.tech/docs/en/operations/table_engines/set/) <!--hide-->