sql - SQL 错误：ORA-00905：缺少关键字，有人可以告诉我以下合并语句有什么问题吗

Question

MERGE INTO table_a PARTITION (x) A
USING (SELECT distinct col1,col2 FROM table_b)b
ON (A.col1=B.col1(+) AND A.col2=B.col2(+))
WHEN MATCHED THEN
UPDATE SET col3='Y'
WHEN NOT MATCHED THEN
UPDATE SET col3='N'; 

Answer 1

该WHEN NOT MATCHED子句无法执行UPDATE- 如果没有找到，它应该更新哪些行？

如果要根据 B 中是否存在现有行来更新 A，一种方法是将 A 拉入合并查询（假设您的表 A 具有主键 PK）：

MERGE INTO table_a PARTITION (x) tgt
  USING (
    SELECT A.PK, B.col1, B.col2 
      FROM table_a A
      LEFT JOIN table_b b ON A.col1 = B.col1 AND A.col2 = B.col2) src
ON (src.pk = tgt.pk)
WHEN MATCHED THEN
  UPDATE SET col3 = (CASE WHEN src.col1 IS NOT NULL THEN 'Y' ELSE 'N' END);