T-SQL批量更新

Question

我正在使用以下脚本从数据库中小批量删除条目：

SET @r = 1;
WHILE @r > 0
BEGIN 
  DELETE TOP (100000)
    [doc].[Document]
    WHERE Id IN (SELECT d.Id FROM @documentIds d); 
  SET @r = @@ROWCOUNT;
END

如何以同样的方式更新 table？我在 T-SQL 中没有 LIMIT 和 OFFSET。我也在考虑性能方面。

Answer 1

您可以从临时 table 更新，然后删除（或使）table 中的行。像这样：

SET @r = 1;
WHILE @r > 0
BEGIN 
    UPDATE d
        SET col = dd.col
        FROM doc.Document d JOIN
             (SELECT TOP 10000 FROM @documents dd ORDER BY id) dd
             ON d.id = dd.id;

    DELETE d TOP 10000 FROM (SELECT TOP 10000 @documents ORDER BY id) d;

    SET @r = @@ROWCOUNT;
END;

Answer 2

这样做。这将每 300 毫秒删除 1000 条记录。但我在这里所做的好处是，我释放了交易，并允许另一个交易完成。因为可能还有另一个 CRUD 语句。此查询不会阻止事务，我用它来 DELETE/UPDATE 生产服务器上的数百万条记录。因为我看到的答案仍然会阻止其他事务，因为该进程仍将附加到会导致高 CPU 和磁盘 IO 的事务。此外，我将 DEADLOCK PRIORITY 设置为低，以便另一个事务具有更高的重要性。它确实需要更长的时间。但这对于服务器成本来说是更安全的，并且不会阻止交易。

SET DEADLOCK_PRIORITY -10

DECLARE @r = 1;

WHILE @r > 0 > 0
BEGIN 
    DELETE TOP (1000)
    [doc].[Document]
    WHERE Id IN (SELECT d.Id FROM @documentIds d); 
    SET @r = @@ROWCOUNT;

    WAITFOR DELAY '00:00:00.300'

END

Answer 3

试试这个，使用开始值和结束值并分批递增

DECLARE @Batch  INT
        ,@StartId BIGINT
        ,@EndId BIGINT
        ,@r     INT

SELECT  @Batch  = 10000
        ,@StartId = 1
        ,@EndId = 0
        ,@r     = 1

WHILE @r > 0
BEGIN 
    SET @StartId = @EndId + 1
    SET @EndId = @EndId + @Batch

    UPDATE d
        SET col = dd.col
        FROM doc.Document d 
        INNER JOIN @documents dd ON d.id = dd.id
            AND dd.id BETWEEN @StartId AND @EndId

    SET @r = @@ROWCOUNT

END

以上方法只有当你有顺序的 id 时才有效，否则使用这种方法预先生成批次并使用它，这将确保每次更新 10000 条记录。

DECLARE @Batch  INT
        ,@StartId BIGINT
        ,@EndId BIGINT
        ,@Cnt INT
        ,@TotalIds INT

DECLARE @Docs TABLE 
(
        StartId BIGINT, 
        EndId BIGINT, 
        BatchID INT
)

SELECT  @Batch  = 10000
        ,@StartId = 1
        ,@EndId = 0
        ,@Cnt = 1
        ,@TotalIds = 0

;WITH CTE_Docs AS
(   SELECT TOP (100) PERCENT id, ROW_NUMBER() OVER (ORDER BY id) as RowID   -- Give seq numbers to each row
    FROM @documentIds d 
)       
-- create batches and batch start and end point
INSERT INTO @Docs(StartId, EndId, BatchId ) 
SELECT  MIN(id) StartID, 
        MAX(id) EndID, 
        (RowID/@Batch)+1 AS BatchID             
FROM CTE_Docs 
GROUP BY RowID/@Batch
ORDER BY BatchID

-- get counter to loop through
SELECT @TotalIds = MAX(BatchID)
FROM @Docs

WHILE @Cnt <= @TotalIds BEGIN   

    SELECT  @StartID    = StartID,
            @EndID      = EndID
    FROM @Docs
    WHERE BatchID = @Cnt

    UPDATE d
        SET col = dd.col
        FROM doc.Document d 
        INNER JOIN @documents dd ON d.id = dd.id
            AND dd.id BETWEEN @StartId AND @EndId

    SET @Cnt = @Cnt + 1

END

希望对您有所帮助。

T-SQL批量更新

Batch update in T-SQL

sql

tsql

sql-server

batch-processing