SQL聚合調用

Question

我有兩個表像

1）客戶

id |  name   
------+------------------- 
    1 | xyz1 
    2 | xyz2 
    3 | xyz3 
    4 | xyz4 
    5 | xyz5 

2）產品

id |  name | customer | state  
------+-------------+----------+------- 
    1 | product 1 | 1  |Shipped  
    2 | product 2 | 1  |Pending 
    3 | product 3 | 1  |Shipped 
    4 | product 4 | 1  |Pending 
    5 | product 5 | 2  |Shipped 

我想有一個查詢是這樣的：

SELECT name from customer, SELECT count(*) from products where state='SHIPPED', SELECT count(*) from product where state='PENDING' for all developers這產量低於上述結果：

name | count_shipped | count_pending  
    -------+---------------+--------------- 
    xyz1 | 2    | 2 
    xyz2 | 1    | 0 
    xyz3 | 0    | 0 
    xyz4 | 0    | 0 
    xyz5 | 0    | 0 

Answer 1

select c.name, 
     sum(case when p.state = 'Pending' then 1 else 0 end) as count_pending, 
     sum(case when p.state = 'Shipped' then 1 else 0 end) as count_shipped 
from customer c 
    left join products p on p.customer = c.id 
group by name; 

Answer 2

SELECT 
    c.id , 
    c.name , 
    SUM(IF p.state = 'Shipped',1,0) AS count_shipped, 
    SUM(IF p.state = 'Pending',1,0) AS count_pending 
FROM Customer AS c 
LEFT JOIN Products AS p ON p.customer = c.id 
GROUP BY c.id 

Answer 3

您還可以使用個性化......

SELECT c.name 
    , COUNT(CASE WHEN state = 'shipped' THEN 'foo' END) count_shipped 
    , COUNT(CASE WHEN state = 'pending' THEN 'foo' END) count_pending 
    FROM customer c 
    LEFT 
    JOIN products p 
    ON p.customer = c.id 
GROUP 
    BY c.id;