标签:null etc who web site -- custom nbsp website
183. Customers Who Never Order
Suppose that a website contains two tables, the Customers
table and the Orders
table. Write a SQL query to find all customers who never order anything.
Table: Customers
.
+----+-------+ | Id | Name | +----+-------+ | 1 | Joe | | 2 | Henry | | 3 | Sam | | 4 | Max | +----+-------+
Table: Orders
.
+----+------------+ | Id | CustomerId | +----+------------+ | 1 | 3 | | 2 | 1 | +----+------------+
Using the above tables as example, return the following:
+-----------+ | Customers | +-----------+ | Henry | | Max | +-----------+
solutions:
SELECT A.Name from Customers A
LEFT JOIN Orders B on a.Id = B.CustomerId
WHERE b.CustomerId is NULL
SELECT A.Name from Customers A WHERE NOT EXISTS (SELECT 1 FROM Orders B WHERE A.Id = B.CustomerId)
SELECT A.Name from Customers A
WHERE A.Id NOT IN (SELECT B.CustomerId from Orders B)
select c.Name from Customers c
where (select count(*) from Orders o where o.customerId=c.id)=0
标签:null etc who web site -- custom nbsp website
原文地址:http://www.cnblogs.com/coskaka/p/7117805.html