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MYSQL ORDER BY

Contexts


The clauses in a SELECT have a specific order:

SELECT ... FROM ... WHERE ... GROUP BY ... HAVING ...
 ORDER BY ... -- goes here
 LIMIT ... OFFSET ...;
( SELECT ... ) UNION ( SELECT ... ) ORDER BY ... -- for ordering the result of the UNION.
SELECT ... GROUP_CONCAT(DISTINCT x ORDER BY ... SEPARATOR ...) ...
ALTER TABLE ... ORDER BY ... -- probably useful only for MyISAM; not for InnoDB

Basic


ORDER BY x

x can be any datatype.

.NULLs precede non-NULLs.
.The default is ASC (lowest to highest)
.Strings (VARCHAR, etc) are ordered according the COLLATION of the declaration
.ENUMs are ordered by the declaration order of its strings.

ASCending / DESCending


ORDER BY x ASC -- same as default
ORDER BY x DESC -- highest to lowest
ORDER BY lastname, firstname -- typical name sorting; using two columns
ORDER BY submit_date DESC -- latest first
ORDER BY submit_date DESC, id ASC -- latest first, but fully specifying order.

.ASC = ASCENDING, DESC = DESCENDING
.NULLs come first even for DESC.
.In the above examples, INDEX(x), INDEX(lastname, firstname), INDEX(submit_date) may significantly improve performance.


But... Mixing ASC and DESC, as in the last example, cannot use a composite index to benefit. Nor will INDEX(submit_date DESC, id ASC) help -- "DESC" is recognized syntactically in the INDEX declaration, but ignored.

Conclusion

In this page (written and validated by ) you learned about MYSQL ORDER BY . What's Next? If you are interested in completing MYSQL tutorial, your next topic will be learning about: MYSQL Group By.



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