歡迎回答我的問題
我從 mysql 開始，我試圖找出 select 陳述句及其用途。
我有帶有這些輸入的表“業務”：
它是這樣制作的：
CREATE TABLE IF NOT EXISTS business(
businessname varchar(250) NOT NULL,
title varchar(250) NOT NULL,
registerdate datetime NOT NULL,
id int NOT NULL,
city varchar(50) NOT NULL,
tk varchar(10) NOT NULL,
number varchar(20) NOT NULL,
branch int,
doy_id int NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (branch) REFERENCES business(id)
ON DELETE CASCADE ON UPDATE CASCADE,
FOREIGN KEY (doy_id) REFERENCES doy(id_kataxorisis)
ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE = InnoDB CHARACTER SET greek COLLATE greek_general_ci;
我想選擇每個企業的 id 和名稱及其分支機構的數量（如果沒有分支機構，我希望它顯示 0）。
ps：我已經想出了如何顯示所有企業及其“父”企業。我不知道它是否會有所幫助，但我是這樣做的：
select c.businessname as child, p.businessname as parent
from business c left join business p on p.id = c.branch
order by c.businessname;
資料是：
INSERT INTO business VALUES
('Vasilopoulos Nikolaos', 'Vasilopoulos','1995-05-20 00:00',26400,'Volos',20004,120,NULL,5),
('Tzatzadaki Maria', 'Tzatzadakis','1992-10-02 00:00',20001,'Patra',24222,58,NULL,2),
('Tzatzadaki Maria', 'Tzatzadakis','1998-08-04 00:00',31200,'Patra',24228,180,20001,3),
('Tzatzadaki Maria', 'Tzatzadakis Ypokatastima 2','1998-08-04 00:00',31201,'Patra',24228,180,31200,3),
('Papadopoulos Ioannis', 'Papadopoulou Mpiskota','2000-01-15 00:00',18777,'Athina',27366,280,NULL,1),
('Kallimani Athanasia', 'Thalassina Kallimanis','2000-03-17 00:00',54874,'Korinthos',22008,71,NULL,4),
('Xristopoulos Ioannis','Chris','2010-05-05 00:00',80000,'Athina',24111,56,NULL,1),
('Kallimani Athanasia', 'Thalassina Kallimanis Kalamatas','2000-03-25 00:00',54875,'Kalamata',25005,23,54874,4),
('Kallimani Athanasia', 'Thalassina Kallimanis Spartis','2000-04-17 00:00',54876,'Sparti',28667,34,54874,4),
('Kallimani Athanasia', 'Thalassina Kallimanis Spartis A tomeas','2000-04-17 00:00',54877,'Sparti',28667,34,54876,4),
('Kallimani Athanasia', 'Thalassina Kallimanis Spartis B tomeas','2000-04-18 00:00',54878,'Sparti',28667,34,54876,4),
('Kallimani Athanasia', 'Thalassina Kallimanis Spartis A tomeas Syskevastirio','2000-04-24 00:00',54879,'Sparti',28667,34,54877,4);
預先感謝您的幫助
uj5u.com熱心網友回復：
不確定您是否想要超過一個級別的分支數，但要獲取父分支及其下面的子分支數將是查詢：
SELECT PB.ID,PB.businessname, COUNT(CB.ID) FROM business PB
LEFT JOIN business CB ON CB.branch = PB.ID
GROUP BY PB.ID,PB.businessname
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