本文例項講述了MySQL使用集合函式進行查詢操作。分享給大家供大家參考，具體如下：

COUNT函式

SELECT COUNT(*) AS cust_num from customers;
SELECT COUNT(c_email) AS email_num FROM customers;
SELECT o_num,COUNT(f_id) FROM orderitems GROUP BY o_num;

SUM函式

SELECT SUM(quantity) AS items_total FROM orderitems WHERE o_num = 30005;
SELECT o_num,SUM(quantity) AS items_total FROM orderitems GROUP BY o_num;

AVG函式

SELECT AVG(f_price) AS avg_price FROM fruits WHERE s_id = 103;
SELECT AVG(f_price) AS avg_price FROM fruits group by s_id;

MAX函式

SELECT MAX(f_price) AS max_price FROM fruits;
SELECT s_id,MAX(f_price) AS max_price FROM fruits GROUP BY s_id;
SELECT MAX(f_name) from fruits;

MIN函式

SELECT MIN(f_price) AS min_price FROM fruits;
SELECT s_id,MIN(f_price) AS min_price FROM fruits GROUP BY s_id;

【例.34】查詢customers表中總的行數

SELECT COUNT(*) AS cust_num from customers;

【例.35】查詢customers表中有電子郵箱的顧客的總數，輸入如下語句：

SELECT COUNT(c_email) AS email_num
FROM customers;

【例.36】在orderitems表中，使用COUNT()函式統計不同訂單號中訂購的水果種類

SELECT o_num,COUNT(f_id) FROM orderitems GROUP BY o_num;

【例.37】在orderitems表中查詢30005號訂單一共購買的水果總量，輸入如下語句：

SELECT SUM(quantity) AS items_total
FROM orderitems
WHERE o_num = 30005;

【例.38】在orderitems表中，使用SUM()函式統計不同訂單號中訂購的水果總量

SELECT o_num,SUM(quantity) AS items_total
FROM orderitems
GROUP BY o_num;

【例.39】在fruits表中，查詢s_id=103的供應商的水果價格的平均值，SQL語句如下：

SELECT AVG(f_price) AS avg_price
FROM fruits
WHERE s_id = 103;

【例.40】在fruits表中，查詢每一個供應商的水果價格的平均值，SQL語句如下：

SELECT s_id,AVG(f_price) AS avg_price
FROM fruits
GROUP BY s_id;

【例.41】在fruits表中查詢市場上價格最高的水果，SQL語句如下：

mysql>SELECT MAX(f_price) AS max_price FROM fruits;

【例7.42】在fruits表中查詢不同供應商提供的價格最高的水果

SELECT s_id,MAX(f_price) AS max_price
FROM fruits
GROUP BY s_id;

【例.43】在fruits表中查詢f_name的最大值，SQL語句如下

SELECT MAX(f_name) from fruits;

【例.44】在fruits表中查詢市場上價格最低的水果，SQL語句如下：

mysql>SELECT MIN(f_price) AS min_price FROM fruits;

【例.45】在fruits表中查詢不同供應商提供的價格最低的水果

SELECT s_id,MIN(f_price) AS min_price
FROM fruits
GROUP BY s_id;

更多關於MySQL相關內容感興趣的讀者可檢視本站專題：《MySQL常用函式大彙總》、《MySQL日誌操作技巧大全》、《MySQL事務操作技巧彙總》、《MySQL儲存過程技巧大全》及《MySQL資料庫鎖相關技巧彙總》

希望本文所述對大家MySQL資料庫計有所幫助。