Editing Select (SQL) (section)

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{{Short description|SQL statement that returns a result set of rows from one or more tables}}
The [[SQL]] '''SELECT''' statement returns a [[result set]] of rows, from one or more [[Table (database)|tables]].<ref>{{cite web |url=http://msdn2.microsoft.com/en-us/library/ms189499.aspx |title=Transact-SQL Syntax Conventions |author=Microsoft |date=23 May 2023 }}</ref><ref>{{cite web |url=http://dev.mysql.com/doc/refman/5.0/en/select.html|title=SQL SELECT Syntax |author=MySQL}}</ref>

A SELECT statement retrieves zero or more rows from one or more [[Database Tables|database tables]] or database [[View (database)|views]]. In most applications, <code>SELECT</code> is the most commonly used [[data manipulation language]] (DML) command. As SQL is a [[declarative programming]] language, <code>SELECT</code> queries specify a result set, but do not specify how to calculate it.  The database translates the query into a "[[query plan]]" which may vary between executions, database versions and database software.  This functionality is called the "[[query optimizer]]" as it is responsible for finding the best possible execution plan for the query, within applicable constraints.

The SELECT statement has many optional clauses:

* <code>SELECT</code> list is the list of [[column (database)|columns]] or SQL expressions to be returned by the query. This is approximately the [[relational algebra]] [[Projection_(relational_algebra)|projection]] operation.
* <code>[[Alias (SQL)|AS]]</code> optionally provides an alias for each column or expression in the <code>SELECT</code> list. This is the relational algebra [[Rename_(relational_algebra)|rename]] operation.
* <code>[[From (SQL)|FROM]]</code> specifies from which table to get the data.<ref>Omitting FROM clause is not standard, but allowed by most major DBMSes.</ref>
* <code>WHERE</code> specifies which rows to retrieve. This is approximately the relational algebra [[Selection_(relational_algebra)|selection]] operation.
* <code>[[Group by (SQL)|GROUP BY]]</code> groups rows sharing a property so that an [[aggregate function]] can be applied to each group.
* <code>[[Having (SQL)|HAVING]]</code> selects among the groups defined by the GROUP BY clause.
* <code>[[Order by (SQL)|ORDER BY]]</code> specifies how to order the returned rows.