更新SQL Server表中所有行的更快方法

Question

有没有更有效的方法来编写这段代码？或者用更少的代码？

SELECT * 
INTO #Temp 
FROM testtemplate

Declare @id INT
Declare @name VARCHAR(127)

WHILE (SELECT Count(*) FROM #Temp) > 0 
BEGIN 

    SELECT TOP 1 @id = testtemplateid FROM #Temp
    SELECT TOP 1 @name = name FROM #Temp

    UPDATE testtemplate
    SET testtemplate.vendortestcode = (SELECT test_code FROM test_code_lookup WHERE test_name = @name)
    WHERE testtemplateid = @id

     --finish processing 
    DELETE #Temp Where testtemplateid = @id
END
DROP TABLE #Temp

Answer 1

您可以在单个UPDATE中执行此操作而无需循环.

UPDATE tt
    SET vendortestcode = tcl.test_code
    FROM testtemplate tt
        INNER JOIN test_code_lookup tcl
            ON tt.name = tcl.test_name

Answer 2

您可以尝试这样的单个更新:

UPDATE A
SET A.vendortestcode = B.test_code
FROM testtemplate A
INNER JOIN test_code_lookup B
ON A.name = B.test_name

此外,您现在的方式是错误的,因为您在两个单独的查询中获取了TOP 1 Id和TOP 1名称,没有ORDER BY,因此不确定您是否为您的ID选择了正确的名称.