Oracle sql MERGE INTO 带有一个 where 子句

Question

我有以下 SQL 代码（这是我到目前为止的代码）：

 MERGE INTO SCHEMA1.TABLE_1 table1 USING
    (
     SELECT DISTINCT table2.column1, 
            view1.column2
     FROM SCHEMA2.TABLE_2 table2
     LEFT JOIN SCHEMA2.VIEW_1 view1
     ON table2.column2 = view1.column3

    ) t2 ON (table1.column3 = t2.column1 )

    WHEN MATCHED THEN
      UPDATE
      SET table1.column4 = t2.column2;

下面是VIEW_1的定义：

    CREATE VIEW SCHEMA_2.VIEW_1
AS (SELECT 
SCHEMA_2.TABLE_1.COLUMN_1, 
SCHEMA_2.TABLE_2.COLUMN_1,
SCHEMA_2.TABLE_2.COLUMN_2,
SCHEMA_2.TABLE_2.COLUMN_3,
SCHEMA_2.TABLE_5.COLUMN_1, 
SCHEMA_2.TABLE_6.COLUMN_1, 
SCHEMA_2.TABLE_6.COLUMN_2,
SCHEMA_2.TABLE_6.COLUMN_3,
SCHEMA_2.TABLE_6.COLUMN_4, 
SCHEMA_2.TABLE_7.COLUMN_1, 
SCHEMA_2.TABLE_7.COLUMN_2, 
SCHEMA_2.TABLE_8.COLUMN_1 
FROM SCHEMA_2.TABLE_1
INNER JOIN SCHEMA_2.TABLE_2
ON SCHEMA_2.TABLE_1.COLUMN_1 = SCHEMA_2.TABLE_2.COLUMN_2 
INNER JOIN SCHEMA_2.TABLE_5
ON SCHEMA_2.TABLE_1.COLUMN_4 = SCHEMA_2.TABLE_5.COLUMN_3
LEFT OUTER JOIN SCHEMA_2.TABLE_6
ON SCHEMA_2.TABLE_2.COLUMN_2 = SCHEMA_2.TABLE_6.COLUMN_4
LEFT OUTER JOIN SCHEMA_2.TABLE_7
ON SCHEMA_2.TABLE_2.COLUMN_1 = SCHEMA_2.TABLE_8.COLUMN_5
);

但我收到以下错误消息：

Error report -
SQL Error: ORA-30926: unable to get a stable set of rows in the source tables
30926. 00000 -  "unable to get a stable set of rows in the source tables"
*Cause:    A stable set of rows could not be got because of large dml

错误原因是什么？在哪里更改代码以使其工作？

感谢您的帮助！

Answer 1

对于此示例，您的问题肯定出在 USING 子查询中。此查询产生多个值 table2.column1:

SELECT DISTINCT table2.column1, 
        view1.column2
 FROM SCHEMA2.TABLE_2 table2
 LEFT JOIN SCHEMA2.VIEW_1 view1
 ON table2.column2 = view1.column3

因此 ON 子句将多次匹配 table1 中的相同行：

ON (table1.column3 = t2.column1 )

Oracle 无法确定应该在 UPDATE 中使用 t2.column2 的哪个值，因此它抛出 ORA-30926.

在子查询中使用 distinct 没有帮助，因为它给出了所有列的排列。您需要编写一个子查询，它将在所有行中生成 t2.column1 的唯一值，或者添加另一个标识列以生成一个可以连接到 table1 的唯一键。

Answer 2

根据我的经验，不仅当USING子句returns more than one for a row for a row in MATCH table时，还会经常返回此错误确定只会返回一行（即使没有返回多行的实际情况）。在这种情况下，为了强制解析器接受查询，我通常会在 MATCH..ON 列上使用 GROUP BY。

MERGE INTO SCHEMA1.TABLE_1 table1 USING
(
 SELECT table2.column1, 
        MAX(view1.column2) as column2
 FROM SCHEMA2.TABLE_2 table2
 LEFT JOIN SCHEMA2.VIEW_1 view1
 ON table2.column2 = view1.column3
 GROUP BY table2.column1
) t2 ON (table1.column3 = t2.column1 )

WHEN MATCHED THEN
  UPDATE
  SET table1.column4 = t2.column2;

Oracle sql MERGE INTO 带有一个 where 子句

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