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* 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
16 lines
752 B
Markdown
16 lines
752 B
Markdown
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machine_translated: true
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machine_translated_rev: 72537a2d527c63c07aa5d2361a8829f3895cf2bd
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---
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# Clause where {#select-where}
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`WHERE` clause permet de filtrer les données en provenance de [FROM](from.md) la clause de `SELECT`.
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Si il y a un `WHERE` , il doit contenir une expression avec la `UInt8` type. C'est généralement une expression avec comparaison et opérateurs logiques. Les lignes où cette expression est évaluée à 0 sont exclues des transformations ou des résultats ultérieurs.
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`WHERE` expression est évaluée sur la possibilité d'utiliser des index et l'élagage de partition, si le moteur de table sous-jacent le prend en charge.
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!!! note "Note"
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Il y a une optimisation de filtrage appelée [prewhere](prewhere.md).
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