试图将 UPDATE 转换为 MERGE

Question

我的问题很简单。我正在尝试将 UPDATE 语句转换为 MERGE 语句以获得更好的性能，因为更新计数可能在 10K - 1M 之间。这是我的更新代码：

UPDATE table_1 t1
   SET t1.col_1 =
          (SELECT t2.name
             FROM table_2 t2
            WHERE t2.fn = t1.col_1),
       t1.Col_3 =
          (SELECT t2.name
             FROM table_2 t2
            WHERE t2.fn = t1.Col_3),
       t1.Col_5 =
          (SELECT t2.name
             FROM table_2 t2
            WHERE t2.fn = t1.Col_5);

我尝试改成MERGE：

MERGE INTO Table_1
     USING (SELECT NAME FROM table_2) A
        ON (1 = 1)
WHEN MATCHED
THEN
   UPDATE SET Table_1.col_1 = A.NAME,
              Table_1.col_3 = A.NAME,
              Table_1.col_5 = A.NAME;

以上代码报错，请帮我解决问题。提前致谢。

Answer 1

使用

WHEN NOT MATCHED THEN
    INSERT (table_1.col1)
    VALUES (a.name);