多CASE语句与否定

考虑以下MySQL的声明：多CASE语句与否定

SELECT costs.cost AS package, payments.cost AS labs, patients.fname, patients.lname, patients.sname, visit.id AS visitid, patients.id, pharm_payments.cost AS pharm_costs ,costs.cost+payments.cost+pharm_payments.cost AS total_cost , 
CASE pharm_payments.cost WHEN pharm_payments.visitid=visit.id THEN pharm_payments.cost 
WHEN pharm_payments.visitid != visit.id THEN 0 
CASE costs.cost WHEN cost.visitid=visit.id THEN costs.cost 
WHEN costs.visitid != visit.id THEN 0 
FROM costs 
LEFT JOIN visit ON costs.visitid = visit.id 
LEFT JOIN patients ON visit.patientid = patients.id 
LEFT JOIN pharm_payments ON pharm_payments.visitid = visit.id 
LEFT JOIN payments ON payments.visitid = visit.id 
WHERE costs.paid = 'not paid' 
AND visit.VisitDate >= CURDATE() 
LIMIT 0 , 30

从查询期望的结果应该是访问ID是哪里不一样，它应该返回零值。我不断收到以下错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CASE costs.cost WHEN cost.visitid=visit.id THEN costs.cost WHEN costs.visitid !=' at line 4

如何解决此错误？

来源

2013-10-28 H Dindi

我不确定'WHEN/THEN'，但它看起来像你可以更容易地实现这个'IF（condition，when_true，when_false）' – Halcyon

为什么你在我这里？ –

你忘了阅读[CASE'的文档]（http://dev.mysql.com/doc/refman/5.7/en/case.html）吗？语法是_right there_。真的很难错过。 –

我不熟悉SQL语句使用case但shouldn't you put an END after?

来源

2013-10-28 10:27:33 D4V1D

我想你case语句应该是这样的：

....... 
CASE 
    WHEN pharm_payments.visitid=visit.id 
    THEN pharm_payments.cost 
    ELSE 0 
END AS Column1, 
CASE 
    WHEN cost.visitid=visit.id 
    THEN costs.cost 
    ELSE 0 
END AS Column2

更新

总结他们你可以这样做：

....... 
(
    CASE 
     WHEN pharm_payments.visitid=visit.id 
     THEN pharm_payments.cost 
     ELSE 0 
    END 
) 
+ 
(
    CASE 
     WHEN cost.visitid=visit.id 
     THEN costs.cost 
     ELSE 0 
    END 
)AS total

来源

2013-10-28 10:27:37 Arion

非常感谢@Arion有什么方法可以总结两个案例的结果，即Column1和Column2？ –

@ user689017：更新答案 – Arion

SELECT 
    costs.cost AS package, 
    payments.cost AS labs, 
    patients.fname, 
    patients.lname, 
    patients.sname, 
    visit.id AS visitid, 
    patients.id, 
    pharm_payments.cost AS pharm_costs, 
    costs.cost + payments.cost + pharm_payments.cost AS total_cost, 
    CASE 
    pharm_payments.cost 
    WHEN pharm_payments.visitid = visit.id 
    THEN pharm_payments.cost 
    WHEN pharm_payments.visitid != visit.id 
    THEN 0 END AS pharm_payments_cost, 
    CASE 
     costs.cost 
     WHEN cost.visitid = visit.id 
     THEN costs.cost 
     WHEN costs.visitid != visit.id 
     THEN 0 END AS costs_cost 
FROM 
    costs 
    LEFT JOIN visit 
    ON costs.visitid = visit.id 
    LEFT JOIN patients 
    ON visit.patientid = patients.id 
    LEFT JOIN pharm_payments 
    ON pharm_payments.visitid = visit.id 
    LEFT JOIN payments 
    ON payments.visitid = visit.id 
WHERE costs.paid = 'not paid' 
    AND visit.VisitDate >= CURDATE() 
LIMIT 0, 30

来源

2013-10-28 10:49:59

多CASE语句与否定

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