SqlServer 利用游标批量更新数据
Intro
游标在有时候会很有用，在更新一部分不多的数据时，可以很方便的更新数据，不需要再写一个小工具来做了，直接写 SQL 就可以了
Sample
下面来看一个实际示例：
-- 声明字段变量
DECLARE @RegionCode INT;
DECLARE @RegionName NVARCHAR(64);
DECLARE @ProvinceId INT;
-- 声明游标
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
);
-- 打开游标
OPEN ProvinceCursor;
-- 移动游标，加载数据
FETCH NEXT FROM ProvinceCursor
INTO @ProvinceId,@RegionCode,@RegionName;
WHILE @@FETCH_STATUS = 0
BEGIN
-- 根据游标数据进行操作，这里只输出要执行的 SQL 脚本，也可以直接 UPDATE，看自己需要
PRINT 'UPDATE dbo.Provinces SET Code = ' + CONVERT(NVARCHAR(12), @RegionCode)+', Name = N'''+@RegionName +''' WHERE Id = ' + CONVERT(NVARCHAR(12), @provinceId) +';';
-- 移动游标到下一条数据
FETCH NEXT FROM ProvinceCursor
INTO @ProvinceId,@RegionCode,@RegionName;
END;
CLOSE ProvinceCursor;
DEALLOCATE ProvinceCursor;
Another Sample
DECLARE @projectId nvarchar(36) -- 声明变量
DECLARE My_Cursor CURSOR --定义游标
FOR (SELECT OriginalProjectId FROM dbo.CommunityProjects
WHERE CommunityId = -1) --查出需要的集合放到游标中
OPEN My_Cursor; --打开游标
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; --关闭游标
DEALLOCATE My_Cursor; --释放游标
and more
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;
More
在做一些小数据量的数据操作时，游标会非常方便，而且游标比较灵活，你可以只生成更新数据的SQL，也可以打印出数据更新前后的值，以便错误更新数据之后的数据恢复