Question

我使用merge语句合并两个表，其中源表中的一行可能会更新目标表中的多行。

有点像这样

MERGE TABLE1 A
USING (SELECT EMP_CODE, DAYS_OFF FROM TABLE2) B
ON (A.ID = B.EMP_CODE)
WHEN MATCHED THEN
UPDATE SET A.DAYS_OFF = B.DAYS_OFF;

然而，当我尝试这个时，我得到SQL Error: ORA-30926: unable to get a stable set of rows in the source tables

我还有其他办法吗？

Answer 1

该错误意味着Oracle无法获取A中的每条记录，这是一组仅与此匹配的记录（例如，一组导致多对多关系的记录）。

您需要做的是在目标表中检查具有相同“ID”的重复项目

SQL> list                
  1  MERGE INTO  TABLE1 A
  2   USING (SELECT * FROM TABLE2) B
  3   ON (A.ID = B.EMP_CODE)
  4   WHEN MATCHED THEN
  5  UPDATE SET A.DAYS_OFF = B.DAYS_OFF
  6*
SQL> r
  1  MERGE INTO  TABLE1 A
  2   USING (SELECT * FROM TABLE2) B
  3   ON (A.ID = B.EMP_CODE)
  4   WHEN MATCHED THEN
  5  UPDATE SET A.DAYS_OFF = B.DAYS_OFF
  6*
MERGE INTO  TABLE1 A
*
ERROR at line 1:
ORA-30926: unable to get a stable set of rows in the source tables

SQL> select id, count(0) from table1 group by id;

        ID   COUNT(0)
---------- ----------
         1          2

SQL> delete from table1 t1 where t1.rowid not in (select max(rowid) from table1 t2 where t2.id = t1.id);

1 row deleted.

SQL> commit;

Commit complete.

SQL> MERGE INTO  TABLE1 A
 USING (SELECT * FROM TABLE2) B
 ON (A.ID = B.EMP_CODE)
 WHEN MATCHED THEN
UPDATE SET A.DAYS_OFF = B.DAYS_OFF  2    3    4    5  ; 

2 rows merged.

SQL> commit;

Commit complete.

Answer 2

我得到SQL错误：ORA-30926：无法获得一组稳定的行源表

因为，您的源表可能包含重复值。

您可能需要再添加一列来唯一标识每一行。

CREATE TABLE source_table (
    col1 NUMBER,
    col2 VARCHAR2(10),
    col3 VARCHAR2(10)
);

INSERT INTO source_table (col1, col2, col3) VALUES (1, 'a', 'w');
INSERT INTO source_table (col1, col2, col3) VALUES (1, 'b', 'x');
INSERT INTO source_table (col1, col2, col3) VALUES (2, 'c', 'y');
INSERT INTO source_table (col1, col2, col3) VALUES (3, 'c', 'z');

COMMIT;

CREATE TABLE target_table (
    col1 NUMBER,
    col2 VARCHAR2(10),
    col3 VARCHAR2(10)
);

INSERT INTO target_table (col1, col2, col3) VALUES (1, 'b', 'z');
INSERT INTO target_table (col1, col2, col3) VALUES (3, 'd', 'w');

COMMIT;

现在我们要合并两个表。

MERGE INTO target_table trg
USING (--Actually we can simply write source_table for this example but I want to write Select:)
       SELECT col1, col2, col3
       FROM source_table 
      ) src 
ON (trg.col1 = src.col1)
WHEN MATCHED THEN UPDATE SET --Don't forget you cannot update columns that included in ON clause
    trg.col2 = src.col2,
    trg.col3 = src.col3
WHEN NOT MATCHED THEN INSERT
    (
        col1,
        col2,
        col3
    )
    VALUES
    (
        src.col1,
        src.col2,
        src.col3
    );

COMMIT;

<强>解决方案

MERGE INTO target_table trg
USING source_table src --Now I simply write the table name:)
ON (
    trg.col1 = src.col1 AND
    trg.col2 = src.col2
   )
WHEN MATCHED THEN UPDATE SET --Don't forget you cannot update columns that included in ON clause
    trg.col3 = src.col3
WHEN NOT MATCHED THEN INSERT
    (
        col1,
        col2,
        col3
    )
    VALUES
    (
        src.col1,
        src.col2,
        src.col3
    );

COMMIT;

PL / SQL - 从源表中的一行更新目标表中的多个行

2 个答案: