Business Information Managment: Introduction to Information Managment by Pitter Taylor & Dr. Vladlena benson kate davis

Author:Pitter Taylor & Dr. Vladlena benson kate davis [Taylor, Pitter & kate davis, Dr. Vladlena benson]
Language: eng
Format: epub
Publisher: UNKNOWN
Published: 2020-09-16T00:00:00+00:00

4 Advanced Selection Queries

4.1 Ordering results

ORDER BY

In a table, the order of the records (rows) cannot be guaranteed – in fact as records are added (to the bottom of the table) and deleted (from the centre of the table) the order becomes even less predictable.

To view a set of ordered records SQL provides the ORDER BY keywords – to see all the records in the PROPERTY table ordered by propertyno use: SELECT *

FROM property

ORDER BY propertyno;

A sort section in a SELECT statement is of the form:

ORDER BY object [DESC [object [DESC]…

Where object can be any valid select list object except *. Numeric values will be shown lowest value first, date values will be shown earliest and character values will be sorted alphabetically. If the DESC keyword is used, sort order will be reversed e.g. highest value first. Note that empty NULL values will always be shown first. The opposite is ASC for ascending. The ORDER BY clause is the last statement of the SELECT command.

ORDER BY examples Activity: In the SQL view of Microsoft Access type in these example queries and verify that they produce similar results.

Examples Display property no, owner no and year income, ordered by year income SELECT propertyno,ownerno, yearincome FROM property

ORDER BY yearincome;

Note that the order by clause can refer to a column not required in the output selection – hence display propertyno and ownerno, ordered by yearincome: SELECT propertyno,ownerno FROM property

ORDER BY yearincome;

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