(mysql.info) selecting-rows

 
 3.3.4.2 Selecting Particular Rows
 .................................
 
 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:
 
      mysql> SELECT * FROM pet WHERE name = 'Bowser';
      +--------+-------+---------+------+------------+------------+
      | name   | owner | species | sex  | birth      | death      |
      +--------+-------+---------+------+------------+------------+
      | Bowser | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
      +--------+-------+---------+------+------------+------------+
 
 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:
 
      mysql> SELECT * FROM pet WHERE birth >= '1998-1-1';
      +----------+-------+---------+------+------------+-------+
      | name     | owner | species | sex  | birth      | death |
      +----------+-------+---------+------+------------+-------+
      | Chirpy   | Gwen  | bird    | f    | 1998-09-11 | NULL  |
      | Puffball | Diane | hamster | f    | 1999-03-30 | NULL  |
      +----------+-------+---------+------+------------+-------+
 
 You can combine conditions, for example, to locate female dogs:
 
      mysql> SELECT * FROM pet WHERE species = 'dog' AND sex = 'f';
      +-------+--------+---------+------+------------+-------+
      | name  | owner  | species | sex  | birth      | death |
      +-------+--------+---------+------+------------+-------+
      | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
      +-------+--------+---------+------+------------+-------+
 
 The preceding query uses the `AND' logical operator. There is also an
 `OR' operator:
 
      mysql> SELECT * FROM pet WHERE species = 'snake' OR species = 'bird';
      +----------+-------+---------+------+------------+-------+
      | 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  |
      +----------+-------+---------+------+------------+-------+
 
 `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 (species = 'cat' AND sex = 'm')
          -> OR (species = 'dog' AND sex = 'f');
      +-------+--------+---------+------+------------+-------+
      | name  | owner  | species | sex  | birth      | death |
      +-------+--------+---------+------+------------+-------+
      | Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
      | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
      +-------+--------+---------+------+------------+-------+
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