我无法使用mysql从具有内部联接的数据库中选择数据 - I cant select data from database with inner join using mysql

I cant select data from database with inner join using mysql

我无法从数据库中选择数据。

下面给出了我的表格结构

客户表

id      name
10      geetha

客户国家/地区表

id    cust_id  country
1       10      6
2       10      16

我得到这样的结果

customer name      country

geetha             6
geetha             16

但我只想一次得到一个客户的数据（不重复）。

customer name      country

geetha             6

我的查询是

SELECT customer.name,customer.id,customer_country.country_id, customer_country.cust_id
    FROM customer
    INNER JOIN customer_country on customer.id = customer_country.cust_id

如果customer_country表中有重复项，则需要选择其中一个。以下是一种使用max():的方法

select c.name, max(cc.country_id)
from customer c inner join
     customer_country cc
     on c.id = cc.cust_id
group by c.name;

如果你想把它们都放在一个列表中，请使用group_concat():

select c.name, group_concat(cc.country_id) as countries
from customer c inner join
     customer_country cc
     on c.id = cc.cust_id
group by c.name;

仅适用于第一条记录，适用于最后：限制1

    SELECT customer.name,customer.id,customer_country.country_id,
    customer_country.cust_id from customer 
    inner join customer_country on customer.id= customer_country.cust_id limit 1

尝试在customer_country.cust_id 之前添加distinct

SELECT customer.name,customer.id,customer_country.country_id, distinct customer_country.cust_id
FROM customer
INNER JOIN customer_country on customer.id = customer_country.cust_id