An ORDER BY clause in SQL specifies that a SQL SELECT statement returns a

result set An SQL result set is a set of rows from a database, as well as metadata about the query such as the column names, and the types and sizes of each column. Depending on the database system In computing, a database is an organized collection of ...

with the rows being sorted by the values of one or more columns. The sort criteria do not have to be included in the result set. The sort criteria can be expressions, including column names, user-defined functions, arithmetic operations, or CASE expressions. The expressions are evaluated and the results are used for the sorting, i.e., the values stored in the column or the results of the function call. ORDER BY is the ''only'' way to sort the rows in the result set. Without this clause, the relational

database system In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spa ...

may return the rows in any order. If an ordering is required, the ORDER BY must be provided in the SELECT statement sent by the application. Although some database systems allow the specification of an ORDER BY clause in subselects or view definitions, the presence there has no effect. A view is a logical relational table, and the relational model mandates that a table is a set of rows, implying no sort order whatsoever. The only exception are constructs like ORDER BY ORDER OF ... (not standardized in SQL:2003) which allow the propagation of sort criteria through nested subselects. The SQL standard's core functionality does not explicitly define a default sort order for

Null Null may refer to: Science, technology, and mathematics Computing * Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value * Null character, the zero-valued ASCII character, also designated by , often use ...

s. With the SQL:2003 extension T611, "Elementary OLAP operations", nulls can be sorted before or after all data values by using the NULLS FIRST or NULLS LAST clauses of the ORDER BY list, respectively. Not all DBMS vendors implement this functionality, however. Vendors who do not implement this functionality may specify different treatments for Null sorting in the DBMS. Structure ORDER BY ... DESC will order in descending order, otherwise ascending order is used. (The latter may be specified explicitly using ASC.)

Examples

SELECT * FROM Employees ORDER BY LastName, FirstName This sorts by the LastName field, then by the FirstName field if LastName matches.

References

SQL keywords Articles with example SQL code {{compu-lang-stub