SQL：where子句中的明显计数？

Question

My order table looks like this:

id   fk_customer
1    34
2    34
3    34
4    7
5    7
6    8

I would like to select only those customers who have more than 2 orders.

This doesnt work however:

SELECT * FROM order WHERE COUNT DISTINCT fk_customer > 2

Please advice!

thanks

Answer 1

Try this:

SELECT fk_customer, COUNT(*)   
FROM dbo.[Order]
GROUP BY fk_customer
HAVING COUNT(*) > 2

Order is a reserved word in most SQL based database systems - bad choice for a table name.... in SQL Server, you need to put it in square brackets to make it clear it's an object name (not the reserved word) to be used.

Answer 2

Try this

SELECT fk_customer FROM orders
GROUP BY fk_customer
HAVING COUNT(id) > 2

Answer 3

If you try to use COUNT in the WHERE clause, SQL will throw an exception. You can only use an aggregate function if it is within a sub-query contained in a HAVING clause or a select list.

SELECT fk_customer, COUNT(*)    
  FROM dbo.[Order] 
 GROUP 
    BY fk_customer 
HAVING COUNT(*) > 2 

Answer 4

SELECT fk_customer, COUNT(fk_customer) FROM [order]
GROUP BY fk_customer HAVING COUNT(*) > 2