🕷️ Crawler Inspector

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Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 89 (from laksa101)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa089.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://clickhouse.com/docs/sql-reference/statements/select/distinct\')), getAhrefsUnparsedNoserviceFromURL(\'https://clickhouse.com/docs/sql-reference/statements/select/distinct\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct","crawl_time":1774594666,"first_indexed_time":1740107262,"http_code":200,"src_unparsed":"com,clickhouse!\/docs\/sql-reference\/statements\/select\/distinct s443","src_root_hash":"12633450985039531489","history_drop_reason":null,"meta_title":"DISTINCT Clause | ClickHouse Docs","meta_descriptions":["Documentation for DISTINCT Clause"],"attrs_boilerpipe_text":"If\nSELECT DISTINCT\nis specified, only unique rows will remain in a query result. Thus, only a single row will remain out of all the sets of fully matching rows in the result.\nYou can specify the list of columns that must have unique values:\nSELECT DISTINCT ON (column1, column2,...)\n. If the columns are not specified, all of them are taken into consideration.\nConsider the table:\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\nUsing\nDISTINCT\nwithout specifying columns:\nSELECT\nDISTINCT\n*\nFROM\nt1\n;\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\nUsing\nDISTINCT\nwith specified columns:\nSELECT\nDISTINCT\nON\n(\na\n,\nb\n)\n*\nFROM\nt1\n;\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\nDISTINCT and ORDER BY\n\nClickHouse supports using the\nDISTINCT\nand\nORDER BY\nclauses for different columns in one query. The\nDISTINCT\nclause is executed before the\nORDER BY\nclause.\nConsider the table:\n┌─a─┬─b─┐\n│ 2 │ 1 │\n│ 1 │ 2 │\n│ 3 │ 3 │\n│ 2 │ 4 │\n└───┴───┘\nSelecting data:\nSELECT\nDISTINCT\na\nFROM\nt1\nORDER\nBY\nb\nASC\n;\n┌─a─┐\n│ 2 │\n│ 1 │\n│ 3 │\n└───┘\nSelecting data with the different sorting direction:\nSELECT\nDISTINCT\na\nFROM\nt1\nORDER\nBY\nb\nDESC\n;\n┌─a─┐\n│ 3 │\n│ 1 │\n│ 2 │\n└───┘\nRow\n2, 4\nwas cut before sorting.\nTake this implementation specificity into account when programming queries.\nNull Processing\n\nDISTINCT\nworks with\nNULL\nas if\nNULL\nwere a specific value, and\nNULL==NULL\n. In other words, in the\nDISTINCT\nresults, different combinations with\nNULL\noccur only once. It differs from\nNULL\nprocessing in most other contexts.\nAlternatives\n\nIt is possible to obtain the same result by applying\nGROUP BY\nacross the same set of values as specified as\nSELECT\nclause, without using any aggregate functions. But there are few differences from\nGROUP BY\napproach:\nDISTINCT\ncan be applied together with\nGROUP BY\n.\nWhen\nORDER BY\nis omitted and\nLIMIT\nis defined, the query stops running immediately after the required number of different rows has been read.\nData blocks are output as they are processed, without waiting for the entire query to finish running.","attrs_markdown":"[Skip to main content](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#__docusaurus_skipToContent_fallback)\n\n[![ClickHouse](https:\/\/clickhouse.com\/docs\/img\/ch_logo_docs.svg)](https:\/\/clickhouse.com\/)\n\n- [Products](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct)\n  \n  - [ClickHouse Cloud Best way to use ClickHouse. 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Available on AWS, GCP, and Azure.](https:\/\/clickhouse.com\/cloud)\n  - [BYOC (Bring Your Own Cloud) The fully managed ClickHouse Cloud service, Can be deployed in your AWS account.](https:\/\/clickhouse.com\/cloud\/bring-your-own-cloud)\n  - [ClickHouse Set up a database with open-source ClickHouse. ClickHouse](https:\/\/clickhouse.com\/clickhouse)\n  - [Discover more than 100 integrations.](https:\/\/clickhouse.com\/integrations)\n  \n  [Discover more than 100 integrations.](https:\/\/clickhouse.com\/integrations)\n- [Use cases](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct)\n  \n  - [Real-time analytics](https:\/\/clickhouse.com\/use-cases\/real-time-analytics)\n  - [Machine Learning & Generative AI](https:\/\/clickhouse.com\/use-cases\/machine-learning-and-data-science)\n  - [Business Intelligence](https:\/\/clickhouse.com\/use-cases\/data-warehousing)\n  - [Logs, Events, Traces](https:\/\/clickhouse.com\/use-cases\/observability)\n  - [All use cases](https:\/\/clickhouse.com\/use-cases)\n  \n  [All use cases](https:\/\/clickhouse.com\/use-cases)\n- [Documentation](https:\/\/clickhouse.com\/docs)\n- [Resources](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct)\n  \n  - [User stories](https:\/\/clickhouse.com\/user-stories)\n  - 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[Syntax](https:\/\/clickhouse.com\/docs\/sql-reference\/syntax)\n  - [Input and Output Formats](https:\/\/clickhouse.com\/docs\/sql-reference\/formats)\n  - [Data types](https:\/\/clickhouse.com\/docs\/sql-reference\/data-types)\n  - [Statements](https:\/\/clickhouse.com\/docs\/sql-reference\/statements)\n    - [SELECT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select)\n      - [ALL](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/all)\n      - [APPLY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/apply-modifier)\n      - [ARRAY JOIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/array-join)\n      - [DISTINCT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct)\n      - [EXCEPT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/except)\n      - [EXCEPT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/except-modifier)\n      - [FORMAT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/format)\n      - [FROM](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/from)\n      - [GROUP BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/group-by)\n      - [HAVING](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/having)\n      - [INTERSECT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/intersect)\n      - [INTO OUTFILE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/into-outfile)\n      - [JOIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/join)\n      - [LIMIT BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit-by)\n      - [LIMIT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit)\n      - [OFFSET](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/offset)\n      - [ORDER BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/order-by)\n      - [PREWHERE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/prewhere)\n      - [QUALIFY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/qualify)\n      - [REPLACE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/replace-modifier)\n      - [SAMPLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/sample)\n      - [UNION](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/union)\n      - [WHERE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/where)\n      - [WITH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/with)\n    - [INSERT INTO](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/insert-into)\n    - [CREATE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/create)\n    - [ALTER](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/alter)\n    - [DELETE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/delete)\n    - [SYSTEM](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/system)\n    - [SHOW](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/show)\n    - [GRANT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/grant)\n    - [EXPLAIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/explain)\n    - [REVOKE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/revoke)\n    - [UPDATE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/update)\n    - [ATTACH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/attach)\n    - [CHECK TABLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/check-table)\n    - [DESCRIBE TABLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/describe-table)\n    - [DETACH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/detach)\n    - [DROP](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/drop)\n    - [EXISTS](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/exists)\n    - [KILL](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/kill)\n    - [OPTIMIZE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/optimize)\n    - [RENAME](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/rename)\n    - [EXCHANGE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/exchange)\n    - [SET](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/set)\n    - [SET ROLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/set-role)\n    - [TRUNCATE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/truncate)\n    - [EXECUTE AS](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/execute_as)\n    - [PARALLEL WITH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/parallel_with)\n    - [USE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/use)\n    - [WATCH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/watch)\n    - [MOVE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/move)\n    - [CHECK GRANT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/check-grant)\n    - [UNDROP](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/undrop)\n  - [Operators](https:\/\/clickhouse.com\/docs\/sql-reference\/operators)\n- [Engines](https:\/\/clickhouse.com\/docs\/engines)\n  - [Database Engines](https:\/\/clickhouse.com\/docs\/engines\/database-engines)\n  - [Table Engines](https:\/\/clickhouse.com\/docs\/engines\/table-engines)\n- [Functions](https:\/\/clickhouse.com\/docs\/sql-reference\/functions)\n  - [Regular functions](https:\/\/clickhouse.com\/docs\/sql-reference\/functions\/regular-functions)\n  - [Aggregate functions](https:\/\/clickhouse.com\/docs\/sql-reference\/aggregate-functions)\n  - [Table functions](https:\/\/clickhouse.com\/docs\/sql-reference\/table-functions)\n  - [Window functions](https:\/\/clickhouse.com\/docs\/sql-reference\/window-functions)\n- [Formats](https:\/\/clickhouse.com\/docs\/interfaces\/formats)\n- [Data Lakes](https:\/\/clickhouse.com\/docs\/sql-reference\/datalakes)\n\n- [Introduction](https:\/\/clickhouse.com\/docs\/sql-reference)\n- [Statements](https:\/\/clickhouse.com\/docs\/sql-reference\/statements)\n- [SELECT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select)\n- DISTINCT\n\n[Edit this page](https:\/\/github.com\/ClickHouse\/ClickHouse\/tree\/master\/docs\/en\/sql-reference\/statements\/select\/distinct.md)\n\n# DISTINCT Clause\nIf `SELECT DISTINCT` is specified, only unique rows will remain in a query result. Thus, only a single row will remain out of all the sets of fully matching rows in the result.\n\nYou can specify the list of columns that must have unique values: `SELECT DISTINCT ON (column1, column2,...)`. If the columns are not specified, all of them are taken into consideration.\n\nConsider the table:\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\nUsing `DISTINCT` without specifying columns:\n```\nSELECT DISTINCT * FROM t1;\n```\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\nUsing `DISTINCT` with specified columns:\n```\nSELECT DISTINCT ON (a,b) * FROM t1;\n```\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\n## DISTINCT and ORDER BY[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#distinct-and-order-by \"Direct link to DISTINCT and ORDER BY\")\nClickHouse supports using the `DISTINCT` and `ORDER BY` clauses for different columns in one query. The `DISTINCT` clause is executed before the `ORDER BY` clause.\n\nConsider the table:\n```\n┌─a─┬─b─┐\n│ 2 │ 1 │\n│ 1 │ 2 │\n│ 3 │ 3 │\n│ 2 │ 4 │\n└───┴───┘\n```\nSelecting data:\n```\nSELECT DISTINCT a FROM t1 ORDER BY b ASC;\n```\n```\n┌─a─┐\n│ 2 │\n│ 1 │\n│ 3 │\n└───┘\n```\nSelecting data with the different sorting direction:\n```\nSELECT DISTINCT a FROM t1 ORDER BY b DESC;\n```\n```\n┌─a─┐\n│ 3 │\n│ 1 │\n│ 2 │\n└───┘\n```\nRow `2, 4` was cut before sorting.\n\nTake this implementation specificity into account when programming queries.\n\n## Null Processing[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#null-processing \"Direct link to Null Processing\")\n`DISTINCT` works with [NULL](https:\/\/clickhouse.com\/docs\/sql-reference\/syntax#null) as if `NULL` were a specific value, and `NULL==NULL`. In other words, in the `DISTINCT` results, different combinations with `NULL` occur only once. It differs from `NULL` processing in most other contexts.\n\n## Alternatives[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#alternatives \"Direct link to Alternatives\")\nIt is possible to obtain the same result by applying [GROUP BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/group-by) across the same set of values as specified as `SELECT` clause, without using any aggregate functions. But there are few differences from `GROUP BY` approach:\n\n- `DISTINCT` can be applied together with `GROUP BY`.\n- When [ORDER BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/order-by) is omitted and [LIMIT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit) is defined, the query stops running immediately after the required number of different rows has been read.\n- Data blocks are output as they are processed, without waiting for the entire query to finish running.\n\n[Previous ARRAY JOIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/array-join)\n\n[Next EXCEPT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/except)\n\n- [DISTINCT and ORDER BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#distinct-and-order-by)\n- [Null Processing](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#null-processing)\n- [Alternatives](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#alternatives)\n\nWas this page helpful?\n\n###### Try ClickHouse Cloud for FREE\nSeparation of storage and compute, automatic scaling, built-in SQL console, and lots more. \\$300 in free credits when signing up.\n\n[Try it for Free](https:\/\/console.clickhouse.cloud\/signUp?loc=doc-card-banner&glxid=7113a784-3608-47e5-8713-9b61fec3a7c0&pagePath=%2Fdocs%2Fsql-reference%2Fstatements%2Fselect%2Fdistinct&origPath=%2Fdocs%2Fsql-reference%2Fstatements%2Fselect%2Fdistinct&utm_ga=GA1.1.143345195.1774594668)\n\n© 2016–2026 ClickHouse, Inc.\n\n[Trademark](https:\/\/clickhouse.com\/legal\/trademark-policy)·[Privacy](https:\/\/clickhouse.com\/legal\/privacy-policy)·[Security](https:\/\/trust.clickhouse.com\/)·[Terms of Service](https:\/\/clickhouse.com\/legal\/agreements\/terms-of-service)\n\n![](https:\/\/static.scarf.sh\/a.png?x-pxid=e6377503-591b-4886-9398-e69c7fee0b91)\n\n© 2016–2026 ClickHouse, Inc.\n\n[Trademark](https:\/\/clickhouse.com\/legal\/trademark-policy)·[Privacy](https:\/\/clickhouse.com\/legal\/privacy-policy)·[Security](https:\/\/trust.clickhouse.com\/)·[Terms of Service](https:\/\/clickhouse.com\/legal\/agreements\/terms-of-service)\n\n![](https:\/\/static.scarf.sh\/a.png?x-pxid=e6377503-591b-4886-9398-e69c7fee0b91)\n\n[![ClickHouse](https:\/\/clickhouse.com\/docs\/img\/ch_logo_docs.svg)](https:\/\/clickhouse.com\/)\n\nEN\n\n- Get started▼\n- Cloud▼\n- Manage data▼\n- Server admin▼\n- Reference▼\n- Integrations▼\n- ClickStack▼\n- chDB▼\n- About▼\n\n[![ClickHouse](https:\/\/clickhouse.com\/docs\/img\/ch_logo_docs.svg)](https:\/\/clickhouse.com\/)\n\nEN\n\nmain-menu\n\n- Introduction▼\n  - 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[HAVING](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/having)\n      - [INTERSECT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/intersect)\n      - [INTO OUTFILE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/into-outfile)\n      - [JOIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/join)\n      - [LIMIT BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit-by)\n      - [LIMIT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit)\n      - [OFFSET](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/offset)\n      - [ORDER BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/order-by)\n      - [PREWHERE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/prewhere)\n      - [QUALIFY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/qualify)\n      - [REPLACE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/replace-modifier)\n      - [SAMPLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/sample)\n      - [UNION](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/union)\n      - [WHERE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/where)\n      - [WITH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/with)\n    - [INSERT INTO](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/insert-into)\n    - CREATE▼\n    - ALTER▼\n    - [DELETE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/delete)\n    - [SYSTEM](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/system)\n    - [SHOW](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/show)\n    - [GRANT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/grant)\n    - [EXPLAIN](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/explain)\n    - [REVOKE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/revoke)\n    - [UPDATE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/update)\n    - [ATTACH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/attach)\n    - [CHECK TABLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/check-table)\n    - [DESCRIBE TABLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/describe-table)\n    - [DETACH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/detach)\n    - [DROP](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/drop)\n    - [EXISTS](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/exists)\n    - [KILL](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/kill)\n    - [OPTIMIZE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/optimize)\n    - [RENAME](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/rename)\n    - [EXCHANGE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/exchange)\n    - [SET](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/set)\n    - [SET ROLE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/set-role)\n    - [TRUNCATE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/truncate)\n    - [EXECUTE AS](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/execute_as)\n    - [PARALLEL WITH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/parallel_with)\n    - [USE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/use)\n    - [WATCH](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/watch)\n    - [MOVE](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/move)\n    - [CHECK GRANT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/check-grant)\n    - [UNDROP](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/undrop)\n  - Operators▼\n- Engines▼\n- Functions▼\n- Formats▼\n- [Data Lakes](https:\/\/clickhouse.com\/docs\/sql-reference\/datalakes)","attrs_readable_markdown":"If `SELECT DISTINCT` is specified, only unique rows will remain in a query result. Thus, only a single row will remain out of all the sets of fully matching rows in the result.\n\nYou can specify the list of columns that must have unique values: `SELECT DISTINCT ON (column1, column2,...)`. If the columns are not specified, all of them are taken into consideration.\n\nConsider the table:\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\nUsing `DISTINCT` without specifying columns:\n```\nSELECT DISTINCT * FROM t1;\n```\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 1 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\nUsing `DISTINCT` with specified columns:\n```\nSELECT DISTINCT ON (a,b) * FROM t1;\n```\n```\n┌─a─┬─b─┬─c─┐\n│ 1 │ 1 │ 1 │\n│ 2 │ 2 │ 2 │\n│ 1 │ 2 │ 2 │\n└───┴───┴───┘\n```\n## DISTINCT and ORDER BY[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#distinct-and-order-by \"Direct link to DISTINCT and ORDER BY\")\nClickHouse supports using the `DISTINCT` and `ORDER BY` clauses for different columns in one query. The `DISTINCT` clause is executed before the `ORDER BY` clause.\n\nConsider the table:\n```\n┌─a─┬─b─┐\n│ 2 │ 1 │\n│ 1 │ 2 │\n│ 3 │ 3 │\n│ 2 │ 4 │\n└───┴───┘\n```\nSelecting data:\n```\nSELECT DISTINCT a FROM t1 ORDER BY b ASC;\n```\n```\n┌─a─┐\n│ 2 │\n│ 1 │\n│ 3 │\n└───┘\n```\nSelecting data with the different sorting direction:\n```\nSELECT DISTINCT a FROM t1 ORDER BY b DESC;\n```\n```\n┌─a─┐\n│ 3 │\n│ 1 │\n│ 2 │\n└───┘\n```\nRow `2, 4` was cut before sorting.\n\nTake this implementation specificity into account when programming queries.\n\n## Null Processing[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#null-processing \"Direct link to Null Processing\")\n`DISTINCT` works with [NULL](https:\/\/clickhouse.com\/docs\/sql-reference\/syntax#null) as if `NULL` were a specific value, and `NULL==NULL`. In other words, in the `DISTINCT` results, different combinations with `NULL` occur only once. It differs from `NULL` processing in most other contexts.\n\n## Alternatives[](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/distinct#alternatives \"Direct link to Alternatives\")\nIt is possible to obtain the same result by applying [GROUP BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/group-by) across the same set of values as specified as `SELECT` clause, without using any aggregate functions. But there are few differences from `GROUP BY` approach:\n\n- `DISTINCT` can be applied together with `GROUP BY`.\n- When [ORDER BY](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/order-by) is omitted and [LIMIT](https:\/\/clickhouse.com\/docs\/sql-reference\/statements\/select\/limit) is defined, the query stops running immediately after the required number of different rows has been read.\n- Data blocks are output as they are processed, without waiting for the entire query to finish running.","meta_canonical":null}

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Page Details

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URL	https://clickhouse.com/docs/sql-reference/statements/select/distinct
Last Crawled	2026-03-27 06:57:46 (13 days ago)
First Indexed	2025-02-21 03:07:42 (1 year ago)
HTTP Status Code	200
Meta Title	DISTINCT Clause \| ClickHouse Docs
Meta Description	Documentation for DISTINCT Clause
Meta Canonical	null
Boilerpipe Text	If SELECT DISTINCT is specified, only unique rows will remain in a query result. Thus, only a single row will remain out of all the sets of fully matching rows in the result. You can specify the list of columns that must have unique values: SELECT DISTINCT ON (column1, column2,...) . If the columns are not specified, all of them are taken into consideration. Consider the table: ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ Using DISTINCT without specifying columns: SELECT DISTINCT * FROM t1 ; ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ Using DISTINCT with specified columns: SELECT DISTINCT ON ( a , b ) * FROM t1 ; ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ DISTINCT and ORDER BY ClickHouse supports using the DISTINCT and ORDER BY clauses for different columns in one query. The DISTINCT clause is executed before the ORDER BY clause. Consider the table: ┌─a─┬─b─┐ │ 2 │ 1 │ │ 1 │ 2 │ │ 3 │ 3 │ │ 2 │ 4 │ └───┴───┘ Selecting data: SELECT DISTINCT a FROM t1 ORDER BY b ASC ; ┌─a─┐ │ 2 │ │ 1 │ │ 3 │ └───┘ Selecting data with the different sorting direction: SELECT DISTINCT a FROM t1 ORDER BY b DESC ; ┌─a─┐ │ 3 │ │ 1 │ │ 2 │ └───┘ Row 2, 4 was cut before sorting. Take this implementation specificity into account when programming queries. Null Processing DISTINCT works with NULL as if NULL were a specific value, and NULL==NULL . In other words, in the DISTINCT results, different combinations with NULL occur only once. It differs from NULL processing in most other contexts. Alternatives It is possible to obtain the same result by applying GROUP BY across the same set of values as specified as SELECT clause, without using any aggregate functions. But there are few differences from GROUP BY approach: DISTINCT can be applied together with GROUP BY . When ORDER BY is omitted and LIMIT is defined, the query stops running immediately after the required number of different rows has been read. Data blocks are output as they are processed, without waiting for the entire query to finish running.
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Thus, only a single row will remain out of all the sets of fully matching rows in the result. You can specify the list of columns that must have unique values: `SELECT DISTINCT ON (column1, column2,...)`. If the columns are not specified, all of them are taken into consideration. Consider the table: ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` Using `DISTINCT` without specifying columns: ``` SELECT DISTINCT * FROM t1; ``` ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` Using `DISTINCT` with specified columns: ``` SELECT DISTINCT ON (a,b) * FROM t1; ``` ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` ## DISTINCT and ORDER BY[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#distinct-and-order-by "Direct link to DISTINCT and ORDER BY") ClickHouse supports using the `DISTINCT` and `ORDER BY` clauses for different columns in one query. The `DISTINCT` clause is executed before the `ORDER BY` clause. Consider the table: ``` ┌─a─┬─b─┐ │ 2 │ 1 │ │ 1 │ 2 │ │ 3 │ 3 │ │ 2 │ 4 │ └───┴───┘ ``` Selecting data: ``` SELECT DISTINCT a FROM t1 ORDER BY b ASC; ``` ``` ┌─a─┐ │ 2 │ │ 1 │ │ 3 │ └───┘ ``` Selecting data with the different sorting direction: ``` SELECT DISTINCT a FROM t1 ORDER BY b DESC; ``` ``` ┌─a─┐ │ 3 │ │ 1 │ │ 2 │ └───┘ ``` Row `2, 4` was cut before sorting. Take this implementation specificity into account when programming queries. ## Null Processing[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#null-processing "Direct link to Null Processing") `DISTINCT` works with [NULL](https://clickhouse.com/docs/sql-reference/syntax#null) as if `NULL` were a specific value, and `NULL==NULL`. In other words, in the `DISTINCT` results, different combinations with `NULL` occur only once. It differs from `NULL` processing in most other contexts. ## Alternatives[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#alternatives "Direct link to Alternatives") It is possible to obtain the same result by applying [GROUP BY](https://clickhouse.com/docs/sql-reference/statements/select/group-by) across the same set of values as specified as `SELECT` clause, without using any aggregate functions. But there are few differences from `GROUP BY` approach: - `DISTINCT` can be applied together with `GROUP BY`. - When [ORDER BY](https://clickhouse.com/docs/sql-reference/statements/select/order-by) is omitted and [LIMIT](https://clickhouse.com/docs/sql-reference/statements/select/limit) is defined, the query stops running immediately after the required number of different rows has been read. - Data blocks are output as they are processed, without waiting for the entire query to finish running. [Previous ARRAY JOIN](https://clickhouse.com/docs/sql-reference/statements/select/array-join) [Next EXCEPT](https://clickhouse.com/docs/sql-reference/statements/select/except) - [DISTINCT and ORDER BY](https://clickhouse.com/docs/sql-reference/statements/select/distinct#distinct-and-order-by) - [Null Processing](https://clickhouse.com/docs/sql-reference/statements/select/distinct#null-processing) - [Alternatives](https://clickhouse.com/docs/sql-reference/statements/select/distinct#alternatives) Was this page helpful? ###### Try ClickHouse Cloud for FREE Separation of storage and compute, automatic scaling, built-in SQL console, and lots more. \$300 in free credits when signing up. 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Readable Markdown	If `SELECT DISTINCT` is specified, only unique rows will remain in a query result. Thus, only a single row will remain out of all the sets of fully matching rows in the result. You can specify the list of columns that must have unique values: `SELECT DISTINCT ON (column1, column2,...)`. If the columns are not specified, all of them are taken into consideration. Consider the table: ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` Using `DISTINCT` without specifying columns: ``` SELECT DISTINCT * FROM t1; ``` ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 1 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` Using `DISTINCT` with specified columns: ``` SELECT DISTINCT ON (a,b) * FROM t1; ``` ``` ┌─a─┬─b─┬─c─┐ │ 1 │ 1 │ 1 │ │ 2 │ 2 │ 2 │ │ 1 │ 2 │ 2 │ └───┴───┴───┘ ``` ## DISTINCT and ORDER BY[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#distinct-and-order-by "Direct link to DISTINCT and ORDER BY") ClickHouse supports using the `DISTINCT` and `ORDER BY` clauses for different columns in one query. The `DISTINCT` clause is executed before the `ORDER BY` clause. Consider the table: ``` ┌─a─┬─b─┐ │ 2 │ 1 │ │ 1 │ 2 │ │ 3 │ 3 │ │ 2 │ 4 │ └───┴───┘ ``` Selecting data: ``` SELECT DISTINCT a FROM t1 ORDER BY b ASC; ``` ``` ┌─a─┐ │ 2 │ │ 1 │ │ 3 │ └───┘ ``` Selecting data with the different sorting direction: ``` SELECT DISTINCT a FROM t1 ORDER BY b DESC; ``` ``` ┌─a─┐ │ 3 │ │ 1 │ │ 2 │ └───┘ ``` Row `2, 4` was cut before sorting. Take this implementation specificity into account when programming queries. ## Null Processing[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#null-processing "Direct link to Null Processing") `DISTINCT` works with [NULL](https://clickhouse.com/docs/sql-reference/syntax#null) as if `NULL` were a specific value, and `NULL==NULL`. In other words, in the `DISTINCT` results, different combinations with `NULL` occur only once. It differs from `NULL` processing in most other contexts. ## Alternatives[](https://clickhouse.com/docs/sql-reference/statements/select/distinct#alternatives "Direct link to Alternatives") It is possible to obtain the same result by applying [GROUP BY](https://clickhouse.com/docs/sql-reference/statements/select/group-by) across the same set of values as specified as `SELECT` clause, without using any aggregate functions. But there are few differences from `GROUP BY` approach: - `DISTINCT` can be applied together with `GROUP BY`. - When [ORDER BY](https://clickhouse.com/docs/sql-reference/statements/select/order-by) is omitted and [LIMIT](https://clickhouse.com/docs/sql-reference/statements/select/limit) is defined, the query stops running immediately after the required number of different rows has been read. - Data blocks are output as they are processed, without waiting for the entire query to finish running.
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