SQL Server：如何更新表b，何時在表a中更新單行？

Question

我創建了一個SQL Server觸發器，當他的一個病人改變狀態爲「殺死」時，應該爲醫生添加一個殺手。但我不知道如何獲得更新的那一行。從現在看來，醫生對於他以前曾經患過的每一位患者都會有耐心的++。

我該如何解決這個問題？

SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 

ALTER TRIGGER [dbo].[PatientKilled] 
ON [dbo].[Patient] 
AFTER UPDATE 
AS 
BEGIN 
    DECLARE 

    SET NOCOUNT ON; 

    UPDATE Doctor 
    SET PatientsKilled += 1 
    FROM Doctor d 
    INNER JOIN inserted p ON d.DoctorId = p.DoctorId 
    WHERE p.PatientState = 'Killed' 
END 

Answer 1

字「殺」意味着醫生是殺人，但無視這個問題本應該做你所需要的。

您應該檢查以前的狀態，並且只在計數器改變時才增加計數器。我認爲「Killed」是一個永久狀態，因此不需要添加邏輯來減少。你應該考慮你是否需要這個。

WITH p AS 
(
SELECT COUNT(*) AS NewKills, 
       I.DoctorId 
FROM INSERTED I JOIN DELETED D 
ON I.PatientId = D.PatientId 
WHERE I.PatientState = 'Killed' 
    AND (D.PatientState <> 'Killed' OR D.PatientState IS NULL) 
GROUP BY I.DoctorId 
) 
UPDATE d 
SET PatientsKilled += NewKills 
FROM Doctor d 
    INNER JOIN p ON d.DoctorId = p.DoctorId 

Answer 2

USE [AD17_Hospital] 
GO 
/****** Object: Trigger [dbo].[PatientKilled] Script Date: 2017-10-21 19:51:32 ******/ 
SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 
ALTER TRIGGER [dbo].[PatientKilled] ON [dbo].[Patient] 
AFTER UPDATE 
AS 
BEGIN 

SET NOCOUNT ON; 
UPDATE Doctor 
SET PatientsKilled (SELECT COUNT(*) FROM Patients WHERE DoctorID = INSERTED.DoctorID AND PatientState = 'Killed') 
FROM Doctor d 

END