Question

我有一张看起来像这样的表：

+-----------------+--------------+
| Field           | Type         |
+-----------------+--------------+
| orderNumber (PK)| int          |
| orderDate       | date         |
| requiredDate    | date         |
| shippedDate     | date         |
| status          | char(15)     |
| comments        | char(200)    |
| customerNumber  | int          |
+-----------------+--------------+

我需要返回具有最大订单数量的customerNumber。

我尝试了以下命令：

SELECT customerNumber FROM ORDERS WHERE customerNumber IN (SELECT customerNumber FROM ORDERS HAVING MAX(COUNT(customerNumber)) GROUP BY customerNumber);

我认为错误：群组功能嵌套太深

Answer 1

SQL Fiddle

Oracle 11g R2架构设置：

CREATE TABLE ORDERS (
  orderNumber     int PRIMARY KEY,
  orderDate       date,
  requiredDate    date,
  shippedDate     date,
  status          char(15),
  comments        char(200),
  customerNumber  int
);

INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 1, 1 );
INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 2, 1 );
INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 3, 2 );
INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 4, 2 );
INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 5, 3 );
INSERT INTO ORDERS ( ORDERNUMBER, CUSTOMERNUMBER ) VALUES ( 6, 4 );

查询1 - 如果您只想获得一个客户：

SELECT CUSTOMERNUMBER
FROM   (
  SELECT CUSTOMERNUMBER,
         COUNT( ORDERNUMBER ) AS num_orders
  FROM   ORDERS
  GROUP BY CUSTOMERNUMBER
  ORDER BY num_orders DESC
)
WHERE ROWNUM = 1

<强> Results ：

| CUSTOMERNUMBER |
|----------------|
|              1 |

查询2 - 如果您希望获得订单数量最多的所有客户：

SELECT CUSTOMERNUMBER
FROM (
  SELECT CUSTOMERNUMBER,
         RANK() OVER ( ORDER BY NUM_ORDERS DESC ) AS RNK
  FROM   (
    SELECT CUSTOMERNUMBER,
           COUNT( ORDERNUMBER ) AS num_orders
    FROM   ORDERS
    GROUP BY CUSTOMERNUMBER
    ORDER BY num_orders DESC
  )
)
WHERE RNK = 1

<强> Results ：

| CUSTOMERNUMBER |
|----------------|
|              1 |
|              2 |

Answer 2

一种方法是使用cte s，在第一个cte中获取订单数，然后选择最大值。最后加入他们以获得最大订单的客户。

with ordercount as (select customernumber, count(distinct ordernumber) ordercount
                   from orders 
                   group by customernumber)
,maxorders as (select max(ordercount) maxcount from ordercount)
select o.customernumber
from ordercount o 
join maxorders m on m.maxcount = o.ordercount

组函数嵌套太深SQL错误

2 个答案: