常用查询例子

在命令行中，选择要操作的数据庫：

  1. shell> mysql your-database-name

创建数据庫表，并往里添加数据：

  1. CREATE TABLE shop (
  2.     article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL,
  3.     dealer  CHAR(20)                 DEFAULT ''     NOT NULL,
  4.     price   DOUBLE(16,2)             DEFAULT '0.00' NOT NULL,
  5.     PRIMARY KEY(article, dealer));
  6. INSERT INTO shop VALUES
  7.     (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),
  8.     (3,'C',1.69),(3,'D',1.25),(4,'D',19.95);

上述语句执行后，有如下结果：

  1. mysql> select * from shop;
  2. +---------+--------+-------+
  3. | article | dealer | price |
  4. +---------+--------+-------+
  5. |    0001 | A      |  3.45 |
  6. |    0001 | B      |  3.99 |
  7. |    0002 | A      | 10.99 |
  8. |    0003 | B      |  1.45 |
  9. |    0003 | C      |  1.69 |
  10. |    0003 | D      |  1.25 |
  11. |    0004 | D      | 19.95 |
  12. +---------+--------+-------+
  13. 7 rows in set (0.01 sec)

查询列特定列中的最大值

  1. SELECT MAX(article) AS article FROM shop;
  3. +---------+
  4. | article |
  5. +---------+
  6. |       4 |
  7. +---------+

简单的子查询：

  1. SELECT article, dealer, price
  2. FROM   shop
  3. WHERE  price=(SELECT MAX(price) FROM shop);
  5. +---------+--------+-------+
  6. | article | dealer | price |
  7. +---------+--------+-------+
  8. |    0004 | D      | 19.95 |
  9. +---------+--------+-------+

也可以通过以下方式来达到同样的效果：

  1. SELECT s1.article, s1.dealer, s1.price
  2. FROM shop s1
  3. LEFT JOIN shop s2 ON s1.price < s2.price
  4. WHERE s2.article IS NULL;
  6. SELECT article, dealer, price
  7. FROM shop
  8. ORDER BY price DESC
  9. LIMIT 1;

每个分组里的最大值

  1. SELECT article, MAX(price) AS price
  2. FROM   shop
  3. GROUP BY article;
  5. +---------+-------+
  6. | article | price |
  7. +---------+-------+
  8. |    0001 |  3.99 |
  9. |    0002 | 10.99 |
  10. |    0003 |  1.69 |
  11. |    0004 | 19.95 |
  12. +---------+-------+

原文: https://strongyoung.gitbooks.io/mysql-reference-manual/content/tutorial/common_queries.html