ordre des tables et plan d'execution

A la lecture du paragraphe ci-dessous,
source : http://download.oracle.com/docs/cd/B...mops.htm#51003

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A join order is the order in which different join items, such as tables, are accessed and joined together. For example, in a join order of table1, table2, and table3, table table1 is accessed first. Next, table2 is accessed, and its data is joined to table1 data to produce a join of table1 and table2. Finally, table3 is accessed, and its data is joined to the result of the join between table1 and table2.

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L'ordre des tables dans la requete est déterminant pour désigner la table directrice lors de la génération du plan d'execution, n'est ce pas ?

Merci de votre interprétation

Non, sauf si vous êtes sur une version d'Oracle qui a plus de 10 ans.

C'est l'optimiseur qui choisit quel est le meilleur ordre à effectuer entre les tables en fonction de la requête et des statistiques.

Dans les cas de jointures externes par contre, l'ordre des tables est forcée par le sens des jointures et l'optimiseur n'intervient pas !
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Bonjour,

Citation:

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Envoyé par totoche

Merci de votre interprétation

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Le text en question par le l'ordre dans le plan d'exécution, pas dans la requête sql.
Cordialement,
Franck.

Remettez votre paragraphe dans le contexte

Citation:

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Many different plans are possible because of the various combinations of different access paths, join methods, and join orders that can be used to access and process data in different ways and produce the same result.

A join order is the order in which different join items, such as tables, are accessed and joined together. For example, in a join order of table1, table2, and table3, table table1 is accessed first. Next, table2 is accessed, and its data is joined to table1 data to produce a join of table1 and table2. Finally, table3 is accessed, and its data is joined to the result of the join between table1 and table2.

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The plan generator explores various plans for a query block by trying out different access paths, join methods, and join orders.

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