SqlServer 利用遊標批量更新數據

時間 2020-02-06

原文原文鏈接

SqlServer 利用遊標批量更新數據

Intro

遊標在有時候會頗有用，在更新一部分很少的數據時，能夠很方便的更新數據，不須要再寫一個小工具來作了，直接寫 SQL 就能夠了html

Sample

下面來看一個實際示例：sql

-- 聲明字段變量
DECLARE @RegionCode INT;
DECLARE @RegionName NVARCHAR(64);
DECLARE @ProvinceId INT;

-- 聲明遊標
DECLARE ProvinceCursor CURSOR FOR(
SELECT Id AS ProvinceId, region.RegionCode,region.RegionName FROM dbo.Provinces AS province
JOIN dbo.Regions AS region ON province.Name=SUBSTRING(region.RegionName,1, LEN(province.Name)) AND region.RegionType=1
);

-- 打開遊標
OPEN ProvinceCursor;

-- 移動遊標，加載數據
FETCH NEXT FROM ProvinceCursor
INTO @ProvinceId,@RegionCode,@RegionName;

WHILE @@FETCH_STATUS = 0
BEGIN
    -- 根據遊標數據進行操做，這裏只輸出要執行的 SQL 腳本，也能夠直接 UPDATE，看本身須要

    PRINT 'UPDATE dbo.Provinces SET Code = ' + CONVERT(NVARCHAR(12), @RegionCode)+', Name = N'''+@RegionName +''' WHERE Id = ' + CONVERT(NVARCHAR(12), @provinceId) +';';
    
        -- 移動遊標到下一條數據
        FETCH NEXT FROM ProvinceCursor
    INTO @ProvinceId,@RegionCode,@RegionName;
END;
CLOSE ProvinceCursor;
DEALLOCATE ProvinceCursor;

Another Sample

DECLARE @projectId nvarchar(36)  -- 聲明變量
DECLARE My_Cursor CURSOR --定義遊標
FOR (SELECT OriginalProjectId FROM dbo.CommunityProjects
WHERE CommunityId = -1) --查出須要的集合放到遊標中
OPEN My_Cursor; --打開遊標
FETCH NEXT FROM My_Cursor INTO @projectId;
WHILE @@FETCH_STATUS = 0
    BEGIN
        UPDATE dbo.CommunityProjects
        SET CommunityId = CAST(ISNULL((
            SELECT ZhongyiCommunityId FROM dbo.CommunityMappings
            WHERE FangdiCommunityId = @projectId
        ),'-1') AS INT)
        WHERE OriginalProjectId = @projectId

        FETCH NEXT FROM My_Cursor INTO @projectId;
    END
CLOSE My_Cursor; --關閉遊標
DEALLOCATE My_Cursor; --釋放遊標

and moreapp

DECLARE @RegionCode INT;
DECLARE @RegionName NVARCHAR(64);
DECLARE @provinceId INT;
DECLARE ProvinceCursor CURSOR FOR(
SELECT RegionCode,
       RegionName
FROM dbo.Regions
WHERE RegionType = 1);
OPEN ProvinceCursor;
FETCH NEXT FROM ProvinceCursor
INTO @RegionCode,
     @RegionName;

WHILE @@FETCH_STATUS = 0
BEGIN
    SET @provinceId =ISNULL((SELECT Id FROM dbo.Provinces WHERE Name = @RegionName), 0);
    IF @provinceId > 0
        PRINT 'UPDATE dbo.Provinces SET Code = ' + CONVERT(NVARCHAR(12), @RegionCode)+' WHERE Id = ' + CONVERT(NVARCHAR(12), @provinceId) +';';
    ELSE
        PRINT 'INSERT INTO dbo.Provinces(Name,Code) VALUES(N''' + @RegionName + ''',' + CONVERT(NVARCHAR(12), @RegionCode)+ ');';
    FETCH NEXT FROM ProvinceCursor
    INTO @RegionCode,
         @RegionName;
END;
CLOSE ProvinceCursor;
DEALLOCATE ProvinceCursor;

在作一些小數據量的數據操做時，遊標會很是方便，並且遊標比較靈活，你能夠只生成更新數據的SQL，也能夠打印出數據更新先後的值，以便錯誤更新數據以後的數據恢復工具