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cd14f9ebcb
ClickHouse/docs/en/sql-reference/statements/select/where.md
Ivan Blinkov cd14f9ebcb
SQL reference refactoring (#10857) 
* split up select.md

* array-join.md basic refactoring

* distinct.md basic refactoring

* format.md basic refactoring

* from.md basic refactoring

* group-by.md basic refactoring

* having.md basic refactoring

* additional index.md refactoring

* into-outfile.md basic refactoring

* join.md basic refactoring

* limit.md basic refactoring

* limit-by.md basic refactoring

* order-by.md basic refactoring

* prewhere.md basic refactoring

* adjust operators/index.md links

* adjust sample.md links

* adjust more links

* adjust operatots links

* fix some links

* adjust aggregate function article titles

* basic refactor of remaining select clauses

* absolute paths in make_links.sh

* run make_links.sh

* remove old select.md locations

* translate docs/es

* translate docs/fr

* translate docs/fa

* remove old operators.md location

* change operators.md links

* adjust links in docs/es

* adjust links in docs/es

* minor texts adjustments

* wip

* update machine translations to use new links

* fix changelog

* es build fixes

* get rid of some select.md links

* temporary adjust ru links

* temporary adjust more ru links

* improve curly brace handling

* adjust ru as well

* fa build fix

* ru link fixes

* zh link fixes

* temporary disable part of anchor checks
2020-05-15 07:34:54 +03:00

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WHERE Clause

WHERE clause allows to filter the data that is coming from FROM clause of SELECT.

If there is a WHERE clause, it must contain an expression with the UInt8 type. This is usually an expression with comparison and logical operators. Rows where this expression evaluates to 0 are expluded from further transformations or result.

WHERE expression is evaluated on the ability to use indexes and partition pruning, if the underlying table engine supports that.

!!! note "Note" There's a filtering optimization called prewhere.