Function
To retrieve information from a database.
Syntax
SELECT [ ALL | DISTINCT ] expression [ [ AS ] alias-name ] | * ...[ FROM table-list ] ...[ WHERE search-condition ] ...[ GROUP BY column-name, ... ] ...[ HAVING search-condition ] ...[ ORDER BY { expression | integer } [ ASC | DESC ], ... ]
Description
The
SELECT
statement retrieves data from the database.
Examples
SELECT * FROM member
Select all values of all tuples from the table member.
SELECT last_name, first_name FROM member ORDER BY last_name, first_name
Selects the values of the last_name and first_name attributes for all tuples in member, and displays them in order by first name within last name.
SELECT last_name, first_name, address FROM member WHERE last_name = 'Copp' ORDER BY last_name, first_name
Selects the values of the last_name, first_name, and address attributes for all tuples where the member's last name is 'Copp'.
SELECT last_name, first_name, address FROM member WHERE last_name like 'C%' ORDER BY last_name, first_name
Selects the values of the last_name, first_name, and address attributes for all tuples where the member's last name begins with a 'C'.
SELECT Date_Borrowed, COUNT( Date_Borrowed ) FROM Borrowed GROUP BY Date_Borrowed WHERE Date_Borrowed >= '1999/01/01' HAVING COUNT( Date_Borrowed ) > 100 ORDER BY Date_Borrowed
Lists the dates and number of books borrowed on those dates for dates after
January 1st, 1999, where the number of books borrowed on that date was more
than 100. The WHERE
clause selects individual tuples, while the
HAVING
clause selects tuples according to their aggregate
values of particular attributes; in this case based upon the COUNT
clause.
SELECT DISTINCT Date_Borrowed FROM Borrowed
Generates a list of unique dates when books were borrowed. No matter how
many times a particular date appears in the Borrowed table,
it appears only once in the output list due to the DISTINCT
keyword. (This can significantly slow a selection down).