SQL SELECT: Difference between revisions
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=Overview= | =Overview= | ||
A query consists in at least one (<code>[[#SELECT|SELECT]]</code>) and at most six categories of [[#Clauses|clauses]] | |||
<font> | |||
[[#SELECT|SELECT]] FROM WHERE GROUP BY HAVING ORDER BY | |||
</font> | |||
Upon execution, an SQL query returns a [[SQL#Result_Set|result set]]. | Upon execution, an SQL query returns a [[SQL#Result_Set|result set]]. | ||
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Query execution. SQL optimizer. Subqueries. | Query execution. SQL optimizer. Subqueries. | ||
Select all (possibly across multiple tables) then filter and discard with where. | Select all (possibly across multiple tables) then filter and discard with where. | ||
Revision as of 23:10, 22 May 2024
Internal
Overview
A query consists in at least one (SELECT) and at most six categories of clauses
SELECT FROM WHERE GROUP BY HAVING ORDER BY
Upon execution, an SQL query returns a result set.
Query execution. SQL optimizer. Subqueries.
Select all (possibly across multiple tables) then filter and discard with where.
Example
SELECT id, name FROM person WHERE id = 1;
Clauses
SELECT
FROM
FROM permanent|derived|temporary|virtual(view)
Table alias.
Querying Multiple Tables
WHERE
GROUP BY ... HAVING
(make sure I understand thoroughly and link)