SQL 查询说明

Question

我有两张表医生和计费。我希望查看治疗一名以上患者的医生的 dname、doctorid 和 sum(fees)。

医生表列如下：

doctorid,dname

帐单列如下：

billid,patientid,doctorid,fees

我尝试了以下代码。但出现错误提示 SQL cmd 未正确结束：

SELECT d.dname,b.doctorid,Sum(b.fees)as "TotalFees" FROM billing b,doctor d ON b.doctorid=d.doctorid
GROUP BY b.doctorid HAVING count(b.patientid)>1; 

我的语法哪里出错了？ 谢谢...

Answer 1

FROM billing b,doctor d ON b.doctorid=d.doctorid 应该是 FROM billing b inner join doctor d ON b.doctorid=d.doctorid

Answer 2

试试这个

SELECT d.dname,b.doctorid,Sum(b.fees)as "TotalFees" FROM billing b inner join doctor d ON b.doctorid=d.doctorid
GROUP BY d.dname,b.doctorid HAVING count(b.patientid)>1; 

Answer 3

您必须在查询中提及您要使用哪个连接，您必须更改您的查询，例如

SELECT d.dname, b.doctorid, Sum(b.fees) as "TotalFees" 
FROM billing b inner join doctor d ON b.doctorid=d.doctorid
GROUP BY d.dname, b.doctorid HAVING count(b.patientid)>1;

查看Join

Answer 4

您缺少INNER JOIN 关键字，并且您还需要GROUP BY 您在SELECT 子句中使用的所有非聚合列（在本例中为GROUP BY d.dname, b.doctorid）。

另外，这可能是一个错字，但Sum(b.fees) 和as 之间没有空格：

SELECT d.dname, b.doctorid, Sum(b.fees) as "TotalFees" 
FROM billing b INNER JOIN doctor d ON b.doctorid=d.doctorid
GROUP BY d.dname, b.doctorid HAVING count(b.patientid)>1; 

请记住，在FROM 子句中使用逗号分隔的表名将执行笛卡尔积，这将成为性能杀手，具体取决于您的 RDBM 优化器。如果您想使用它，请记住将其连接条件放在 WHERE 子句中（ON 子句与 JOIN 语法一起使用）：

SELECT d.dname, b.doctorid, Sum(b.fees) as "TotalFees" 
FROM billing b, doctor d 
WHERE b.doctorid = d.doctorid
GROUP BY d.dname, b.doctorid HAVING count(b.patientid)>1;