SQL查询澄清

Question

我有两张桌子医生和账单。我希望查看治疗一名以上病人的医生的dname，doctorid和总和（费用）。

医生表栏如下：

doctorid,dname

结算表格列如下：

billid,patientid,doctorid,fees

我尝试了以下代码。但得到一个错误，指出SQL cmd没有正确结束：

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; 

我的语法出错了？ 感谢...

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

您错过了INNER JOIN关键字，还需要GROUP BY SELECT子句中GROUP BY d.dname, b.doctorid子句中使用的所有非汇总列Sum(b.fees)这种情况）。

此外，它可能是拼写错误，但您在as和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; 之间没有空格：

FROM

请记住，在WHERE子句中使用逗号分隔的表名将执行笛卡尔积，这将是性能杀手，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ON子句中（JOIN子句与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; 语法一起使用）：

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Answer 3

您必须在查询中提及您要使用的联接，您必须更改您的查询，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;

检查Join

Answer 4

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;