本文實例講述了MySQL使用集合函數進行查詢操作。分享給大家供大家參考，具體如下：
COUNT函數
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函數
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函數
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函數
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函數
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()函數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()函數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表中查找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表中查找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表中查找f_name的最大值，SQL語句如下
SELECT MAX(f_name) from fruits;
【例.44】在fruits表中查找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表中查找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;
更多關于MySQL相關內容感興趣的讀者可查看本站專題：《MySQL常用函數大匯總》、《MySQL日志操作技巧大全》、《MySQL事務操作技巧匯總》、《MySQL存儲過程技巧大全》及《MySQL數據庫鎖相關技巧匯總》
希望本文所述對大家MySQL數據庫計有所幫助。
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