带有条件语句的 SQL INSERT IF THEN ELSE

Question

我正在尝试将值从一个表合并到另一个表。其中一个值是条件值，但看起来我没有正确理解语法。最初，我使用的是 IF-THEN-ELSE 语句，但被建议改用 CASE 语句。

这是失败的语法要点：

CREATE PROCEDURE EmployeeMerge
AS 
BEGIN
    SET NOCOUNT ON;
    MERGE INTO Employee AS t1  
    USING 
        (SELECT 
               EmployeeName,
               Zip,
               UpdateDate 
        FROM table2) AS t2
        ON (t1.EmployeeID = t2.EmployeeID)
    WHEN MATCHED AND t2.UpdatedDate > t1.UpdatedDate THEN 
        UPDATE 
        SET 
            t1.EmployeeName = s.EmployeeName, 
            t1.Zip =
                (CASE 
                    WHEN t2.ZipExt IS NULL OR t2.ZipExt = '' THEN t2.Zip 
                    ELSE (t2.Zip + '-' + t2.ZipExt)
                END),
            t1.UpdatedDate = t2.UpdateDate
    WHEN NOT MATCHED THEN
        INSERT (EmployeeName,  
            Zip,  
            ModDate)
        VALUES 
            (t2.Name, 
            (CASE 
                WHEN t2.ZipExt IS NULL OR t2.ZipExt = '' THEN t2.Zip 
                ELSE (t2.Zip + '-' + t2.Zip_Ext)
            END),
            t2.UpdatedDate)
    OUTPUT 
        deleted.*, 
        $action, 
        inserted.* 
END; **-- A MERGE statement must be terminated by a semi-colon (;)**
GO

如果我不实现条件，即简单地设置 t1.Zip = t2.Zip，则此 MERGE 语句可以正常工作，但当然，这是避免 t2.ZipExt 字段。

Answer 1

MERGE 语句必须以分号 (;) 结束

您没有用分号终止 MERGE。您已终止 BEGIN-END。移动分号。

Answer 2

我从来没有真正关心过合并命令。有时我可以看到使用它，但在大多数情况下，它比我喜欢的 SQL 更复杂。

UPDATE e
SET     e.EmployeeName=t1.EmployeeName
    ,   e.Zip=CASE 
                WHEN t1.ZipExt IS NULL OR t1.ZipExt = '' THEN t1.Zip 
                ELSE (t1.Zip + '-' + t1.ZipExt)
            END
    ,   e.UpdatedDate=t1.UpdatedDate
FROM Employee e
INNER JOIN Table t1 ON e.EmployeeID = t1.EmployeeID
WHERE t1.UpdatedDate > e.UpdatedDate

INSERT INTO Employee (EmployeeName,Zip,UpdatedDate)
    SELECT
            t1.EmployeeName
        ,   t1.Zip=CASE 
                WHEN t1.ZipExt IS NULL OR t1.ZipExt = '' THEN t1.Zip 
                ELSE (t1.Zip + '-' + t1.ZipExt)
            END
        ,   t1.UpdatedDate
    FROM Table t1
    LEFT JOIN Employee e ON e.EmployeeID = t1.EmployeeID
    WHERE e.EmployeeID IS NULL