SQL Server解决游标性能问题的替代方案

DECLARE @EmployeeID INT;
DECLARE @Salary DECIMAL(18, 2);
 
-- 创建一个临时表来存储需要处理的数据
SELECT EmployeeID, Salary
INTO #TempEmployees
FROM Employees;
 
-- 初始化变量
SET @EmployeeID = (SELECT MIN(EmployeeID) FROM #TempEmployees);
 
WHILE @EmployeeID IS NOT NULL
BEGIN
    -- 获取当前行的数据
    SELECT @Salary = Salary
    FROM #TempEmployees
    WHERE EmployeeID = @EmployeeID;
 
    -- 更新工资
    UPDATE Employees
    SET Salary = @Salary * 1.1 -- 假设给每个员工加薪 10%
    WHERE EmployeeID = @EmployeeID;
 
    -- 移动到下一行
    SET @EmployeeID = (SELECT MIN(EmployeeID) FROM #TempEmployees WHERE EmployeeID > @EmployeeID);
END;
 
-- 删除临时表
DROP TABLE #TempEmployees;

UPDATE EmployeesSET Salary = Salary * 1.1;

WITH RankedEmployees AS (
    SELECT 
        EmployeeID,
        Salary,
        ROW_NUMBER() OVER (ORDER BY EmployeeID) AS RowNum
    FROM Employees
)
UPDATE RankedEmployees
SET Salary = Salary * 1.1
WHERE RowNum <= 10; -- 假设只更新前 10 名员工

MERGE TargetEmployees AS target
USING SourceEmployees AS source
ON target.EmployeeID = source.EmployeeID
WHEN MATCHED THEN
    UPDATE SET
        target.Salary = source.Salary,
        target.Department = source.Department
WHEN NOT MATCHED THEN
    INSERT (EmployeeID, Salary, Department)
    VALUES (source.EmployeeID, source.Salary, source.Department)
WHEN NOT MATCHED BY SOURCE THEN
    DELETE;

DECLARE @TempEmployees TABLE (
    EmployeeID INT,
    Salary DECIMAL(18, 2)
);
 
-- 将需要处理的数据插入表变量
INSERT INTO @TempEmployees (EmployeeID, Salary)
SELECT EmployeeID, Salary
FROM Employees;
 
DECLARE @EmployeeID INT;
DECLARE @Salary DECIMAL(18, 2);
 
-- 初始化变量
SET @EmployeeID = (SELECT MIN(EmployeeID) FROM @TempEmployees);
 
WHILE @EmployeeID IS NOT NULL
BEGIN
    -- 获取当前行的数据
    SELECT @Salary = Salary
    FROM @TempEmployees
    WHERE EmployeeID = @EmployeeID;
 
    -- 更新工资
    UPDATE Employees
    SET Salary = @Salary * 1.1 -- 假设给每个员工加薪 10%
    WHERE EmployeeID = @EmployeeID;
 
    -- 移动到下一行
    SET @EmployeeID = (SELECT MIN(EmployeeID) FROM @TempEmployees WHERE EmployeeID > @EmployeeID);
END;

SELECT 
    e.EmployeeID,
    e.Name,
    r.ReportContent
FROM Employees e
CROSS APPLY dbo.GenerateReport(e.EmployeeID) r;