SQL SELECT: Difference between revisions
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A query consists in at least one (<code>[[#SELECT|SELECT]]</code>) and at most six categories of [[#Clauses|clauses]]: | A query consists in at least one (<code>[[#SELECT|SELECT]]</code>) and at most six categories of [[#Clauses|clauses]]: | ||
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[[#SELECT|SELECT]] [ | [[#SELECT|SELECT]] [<font color=darkgray>one or more things</font>] [[#FROM|FROM]] [...] [[#WHERE|WHERE]] [...] [[SQL_GROUP_BY#Overview|GROUP BY]] [...] [[SQL_GROUP_BY#Overview|HAVING]] [...] [[#ORDER_BY|ORDER BY]] [...]; | ||
</font> | </font> | ||
Revision as of 23:18, 22 May 2024
Internal
Overview
A query consists in at least one (SELECT) and at most six categories of clauses:
SELECT [one or more things] FROM [...] WHERE [...] GROUP BY [...] HAVING [...] ORDER BY [...];
Almost every query will include at least three of these clauses (SELECT, FROM and WHERE).
Upon execution, an SQL query returns a result set.
Select all (possibly across multiple tables) then filter and discard with where.
Example
SELECT id, name FROM person WHERE id = 1;
The following query:
SELECT;
is valid, it returns one empty row.
Clauses
SELECT
FROM
FROM permanent|derived|temporary|virtual(view)
Table alias.