Question

我需要找到提供最多服务的机组负责人。我有下表：

CREATE TABLE JasperGreen.PROVIDED_SERVICE (
    PROVISION INT AUTO_INCREMENT NOT NULL,
    CONTRACT_ID INT NOT NULL,
    PROVISION_DATE DATE NOT NULL,
    CREW_CHIEF INT NOT NULL,
    CUST_ID INT NOT NULL,
    CONSTRAINT PROVIDED_SERVICE_FK1 FOREIGN KEY(CUST_ID) REFERENCES CUSTOMER(CUST_ID),
    CONSTRAINT PROVIDED_SERVICE_FK2 FOREIGN KEY(CONTRACT_ID) REFERENCES CONTRACTED_SERVICE(CONTRACT_ID),
    CONSTRAINT PROVIDED_SERVICE_PK PRIMARY KEY (PROVISION)
);

到目前为止，我运行了此查询并返回错误：

SELECT CREW_CHIEF, COUNT(provision)
FROM PROVIDED_SERVICE
WHERE provision = 
    (SELECT MAX(COUNT(provision)) FROM PROVIDED_SERVICE)

错误1111：无效使用组功能。

有什么想法吗？

Answer 1

select CREW_CHIEF, count(provision)
from PROVIDED_SERVICE
GROUP BY CREW_CHIEF
ORDER BY count(provision) DESC
LIMIT 1

您无法嵌套MAX和COUNT。如果你想使用你的方法，需要通过

添加组

select CREW_CHIEF, count(provision)
from PROVIDED_SERVICE
group by CREW_CHIEF
HAVING count(provision) = 
       (select count(provision)  
        from PROVIDED_SERVICE
        group by CREW_CHIEF
        order by count(provision) desc
        limit 1
       )

编辑：

蒂姆指出。第一个查询返回一个随机厨师，以防万一。第二个返回所有厨师与最大数量的关系。

Answer 2

如果你只想要一位顶级厨师，胡安的回答是好的，或者，如果你想获得第一名，你就不会关心哪位厨师会回来。继续您目前的方法，我们可以让所有厨师都处于第一位，包括领带：

SELECT CREW_CHIEF, COUNT(*) AS cnt
FROM PROVIDED_SERVICE
GROUP BY CREW_CHIEF
HAVING COUNT(*) = (
    SELECT MAX(cnt) FROM (
        SELECT COUNT(*) AS cnt FROM PROVIDED_SERVICE GROUP BY CREW_CHIEF) t );

如何找到提供最多服务的crew_chief？

2 个答案:

Demo