Retrieving Information from a Table The  UPDATE  changes only the record in question and does not require you to reload the table. There is an exception to the principle that  SELECT *  selects all columns. If a table contains invisible columns,  *  does not include them. For more information, see Section 13.1.20.10, “Invisible Columns” . As shown in the preceding section, it is easy to retrieve an entire table. Just omit the  WHERE  clause from the  SELECT  statement. But typically you don’t want to see the entire table, particularly when it becomes large. Instead, you’re usually more interested in answering a particular question, in which case you specify some constraints on the information you want. Let’s look at some selection queries in terms of questions about your pets that they answer. You can select only particular rows from your table. For example, if you want to verify the change that you made to Bowser’s birth date, select Bowser’s record like this: The output confirms that the year is correctly recorded as 1989, not 1979. String comparisons normally are case-insensitive, so you can specify the name as  ’bowser’ ,  ’BOWSER’ , and so forth. The query result is the same. You can specify conditions on any column, not just  name . For example, if you want to know which animals were born during or after 1998, test the  birth  column: You can combine conditions, for example, to locate female dogs: The preceding query uses the  AND  logical operator. There is also an  OR  operator: AND  and  OR  may be intermixed, although  AND  has higher precedence than  OR . If you use both operators, it is a good idea to use parentheses to indicate explicitly how conditions should be grouped: mysql>  SELECT * FROM pet WHERE name = ’Bowser’; mysql>  SELECT * FROM pet WHERE birth >= ’1998-1-1’; mysql>  SELECT * FROM pet WHERE species = ’dog’ AND sex = ’f’; mysql>  SELECT * FROM pet WHERE species = ’snake’ OR species = ’bird’; 3.3.4.2 Selecting Particular Rows +--------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+-------+---------+------+------------+------------+ | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | +--------+-------+---------+------+------------+------------+ +----------+-------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+-------+ | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Puffball | Diane | hamster | f | 1999-03-30 | NULL | +----------+-------+---------+------+------------+-------+ +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ +----------+-------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+-------+ | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | | Slim | Benny | snake | m | 1996-04-29 | NULL | +----------+-------+---------+------+------------+-------+ 313