實例

以下是如何解決MySQL的一些常見問題的示例。

首先創建一個表，并且導入數據

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

檢索表中的全部數據

select * from shop; +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | article | dealer | price | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | 0001 | A | 3.45 | | 0001 | B | 3.99 | | 0002 | A | 10.99 | | 0003 | B | 1.45 | | 0003 | C | 1.69 | | 0003 | D | 1.25 | | 0004 | D | 19.95 | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+

求某一列的最大值或者 最小值

SELECT MAX(article) AS article FROM shop; +‐‐‐‐‐‐‐‐‐+ | article | +‐‐‐‐‐‐‐‐‐+ | 4 | +‐‐‐‐‐‐‐‐‐+ //求某一列的最小值 select min(price) as article from shop; +‐‐‐‐‐‐‐‐‐+ | article | +‐‐‐‐‐‐‐‐‐+ | 1.25 | +‐‐‐‐‐‐‐‐‐+

過濾出某個字段值最大的整條記錄數據-涉及到子查詢?

SELECT article, dealer, price FROM shop WHERE price=(SELECT MAX(price) FROM shop); +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | article | dealer | price | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | 0004 | D | 19.95 | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+

也可以通過關聯查詢來進行檢索

SELECT s1.article, s1.dealer, s1.price FROM shop s1 LEFT JOIN shop s2 ON s1.price < s2.price WHERE s2.article IS NULL; SELECT article, dealer, price FROM shop ORDER BY price DESC LIMIT 1;

求出每一列的最大值，并且根據某一個字段進行分組--分組topn求法

SELECT article, MAX(price) AS price FROM shop GROUP BY article; +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | article | price | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | 0001 | 3.99 | | 0002 | 10.99 | | 0003 | 1.69 | | 0004 | 19.95 | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+

另一種寫法

SELECT article, dealer, price FROM shop s1 WHERE price=(SELECT MAX(s2.price) FROM shop s2 WHERE s1.article = s2.article); +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | article | dealer | price | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+ | 0001 | B | 3.99 | | 0002 | A | 10.99 | | 0003 | C | 1.69 | | 0004 | D | 19.95 | +‐‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐‐+‐‐‐‐‐‐‐+

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