SqlServer 利用游標批量更新數據
Intro
游標在有時候會很有用，在更新一部分不多的數據時，可以很方便的更新數據，不需要再寫一個小工具來做了，直接寫 SQL 就可以了
Sample
下面來看一個實際示例：
-- 聲明字段變量
DECLARE @RegionCode INT;
DECLARE @RegionName NVARCHAR(64);
DECLARE @ProvinceId INT;
-- 聲明游標
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
);
-- 打開游標
OPEN ProvinceCursor;
-- 移動游標，加載數據
FETCH NEXT FROM ProvinceCursor
INTO @ProvinceId,@RegionCode,@RegionName;
WHILE @@FETCH_STATUS = 0
BEGIN
-- 根據游標數據進行操作，這里只輸出要執行的 SQL 腳本，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) +';';
-- 移動游標到下一條數據
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 --定義游標
FOR (SELECT OriginalProjectId FROM dbo.CommunityProjects
WHERE CommunityId = -1) --查出需要的集合放到游標中
OPEN My_Cursor; --打開游標
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; --關閉游標
DEALLOCATE My_Cursor; --釋放游標
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
在做一些小數據量的數據操作時，游標會非常方便，而且游標比較靈活，你可以只生成更新數據的SQL，也可以打印出數據更新前后的值，以便錯誤更新數據之后的數據恢復