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The simplest form of SELECT
retrieves everything from a table:
mysql> SELECT * FROM pet; +----------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+--------+---------+------+------------+------------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Fang | Benny | dog | m | 1990-08-27 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | | Slim | Benny | snake | m | 1996-04-29 | NULL | | Puffball | Diane | hamster | f | 1999-03-30 | NULL | +----------+--------+---------+------+------------+------------+ |
This form of SELECT
is useful if you want to review your entire table,
for instance, after you've just loaded it with your initial dataset. For
example, you may happen to think that the birth date for Bowser doesn't seem
quite right. Consulting your original pedigree
papers, you find that the correct birth year should be 1989, not 1979.
There are least a couple of ways to fix this:
DELETE
and LOAD DATA
:
mysql> DELETE FROM pet; mysql> LOAD DATA LOCAL INFILE "pet.txt" INTO TABLE pet; |
However, if you do this, you must also re-enter the record for Puffball.
UPDATE
statement:
mysql> UPDATE pet SET birth = "1989-08-31" WHERE name = "Bowser"; |
The UPDATE
changes only the record in question and does not require you
to reload the table.