本文實(shí)例講述了MySQL使用集合函數(shù)進(jìn)行查詢(xún)操作。分享給大家供大家參考，具體如下：
COUNT函數(shù)
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(shù)
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(shù)
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(shù)
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(shù)
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(xún)customers表中總的行數(shù)
SELECT COUNT(*) AS cust_num from customers;
【例.35】查詢(xún)customers表中有電子郵箱的顧客的總數(shù)，輸入如下語(yǔ)句：
SELECT COUNT(c_email) AS email_num
FROM customers;
【例.36】在orderitems表中，使用COUNT()函數(shù)統(tǒng)計(jì)不同訂單號(hào)中訂購(gòu)的水果種類(lèi)
SELECT o_num, COUNT(f_id) FROM orderitems GROUP BY o_num;
【例.37】在orderitems表中查詢(xún)30005號(hào)訂單一共購(gòu)買(mǎi)的水果總量，輸入如下語(yǔ)句：
SELECT SUM(quantity) AS items_total
FROM orderitems
WHERE o_num = 30005;
【例.38】在orderitems表中，使用SUM()函數(shù)統(tǒng)計(jì)不同訂單號(hào)中訂購(gòu)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(xún)s_id=103的供應(yīng)商的水果價(jià)格的平均值，SQL語(yǔ)句如下：
SELECT AVG(f_price) AS avg_price
FROM fruits
WHERE s_id = 103;
【例.40】在fruits表中，查詢(xún)每一個(gè)供應(yīng)商的水果價(jià)格的平均值，SQL語(yǔ)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(chǎng)上價(jià)格最高的水果，SQL語(yǔ)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(yīng)商提供的價(jià)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(yǔ)句如下
SELECT MAX(f_name) from fruits;
【例.44】在fruits表中查找市場(chǎng)上價(jià)格最低的水果，SQL語(yǔ)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(yīng)商提供的價(jià)格最低的水果
SELECT s_id, MIN(f_price) AS min_price
FROM fruits
GROUP BY s_id;
更多關(guān)于MySQL相關(guān)內(nèi)容感興趣的讀者可查看本站專(zhuān)題：《MySQL常用函數(shù)大匯總》、《MySQL日志操作技巧大全》、《MySQL事務(wù)操作技巧匯總》、《MySQL存儲(chǔ)過(guò)程技巧大全》及《MySQL數(shù)據(jù)庫(kù)鎖相關(guān)技巧匯總》
希望本文所述對(duì)大家MySQL數(shù)據(jù)庫(kù)計(jì)有所幫助。
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