sql-比较表

Question

如何比较两个表并根据结果做出反应。 例如，我有2个表（精确的结构）：tableA（键，文本）和tableB（键，文本）以及结果表（键，字段，大小写）。

if key is in tableA, but not in tableB --> case: insert
if key is in tableB, but not in tableA --> case: delete
if key is in tableA and in tableB, but the text is different -> update
if key is in tableA and in tableB, and the text is the same -> nothing

结果表如下所示：

key | text | case
------------------
1   |  t1  | update
2   |  t2  | delete
3   |  t3  | insert
4   |  t4  | nothing

仅用一个查询就能做到吗？

获得插入（删除则相反）：

SELECT key FROM tableA
MINUS
SELECT key FROM tableB;

Answer 1

我认为您需要这样的东西：

  select 'IN Table1, NOT Table2', Key_column
    from user_tab_columns
   where table_name = 'Table1'
  MINUS
  select 'IN Table1, NOT Table2', Key_column
    from user_tab_columns
   where table_name = 'Table2'
  )
  UNION ALL
  (
  select 'IN Table2, NOT Table1', Key_column
    from user_tab_columns
   where table_name = 'Table2'
  MINUS
  select 'IN Table2, NOT Table1', Key_column
    from user_tab_columns
   where table_name = 'Table1'
  )

您可以在以下链接中找到此概念的一些示例和变体： http : //asktom.oracle.com/pls/asktom/f?p=100 :11:0 :::::P11_QUESTION_ID : 1004115105172

祝好运。

Answer 2

这会有所帮助吗？

SELECT NVL (a.key, b.key) AS "KEY",
       NVL (a.text, b.text) as "TEXT",
       CASE
          WHEN a.key IS NOT NULL AND b.key IS NULL THEN
             'Insert'
          WHEN a.key IS NULL AND b.key IS NOT NULL THEN
             'Delete'
          WHEN a.key IS NOT NULL AND b.key IS NOT NULL AND a.text != b.text THEN
             'Update'
          WHEN a.key IS NOT NULL AND b.key IS NOT NULL AND a.text = b.text THEN
             'Nothing'
       END
          "CASE"
  FROM tablea a FULL OUTER JOIN tableb b ON a.key = b.key;