合并多个选择语句输出

Question

I have list of view in an excel. I have to check whether they are present in the DB or not. Is there any way to write an query to get this done.

Right now I am querying ALL_VIEWS to know whether a view is present or not.

select VIEW_NAME from ALL_VIEWS where VIEW_NAME = 'ABC_V_DEF';

Do I need to execute the above statement for all the view present with me or there is query? I am thinking to combine select query output to get this done. The output may look like... Please suggest...

+-----------------------------
|  `VIEW_NAME`|`View Present?|
+----------------------------+
|  ABC_V_DEF  |    Yes       |
|  ABC_V_XCV  |     No       |
|      .      |     .        |
|      .      |     .        |
+-------------+--------------+

Answer 1

You can construct the select queries inside the o inline view from the list of views in excel and then run it like this.

SELECT o.view_name,
       CASE
         WHEN EXISTS (SELECT 1
                      FROM   all_views a
                      WHERE  a.view_name = o.view_name) THEN 'Yes'
         ELSE 'No'
       END "View Present?"
FROM   (SELECT 'ABC_V_DEF' VIEW_NAME
        FROM   dual
        UNION ALL
        SELECT 'ABC_V_DEF2' VIEW_NAME
        FROM   dual
        UNION ALL
        SELECT 'ABC_V_DEF3' VIEW_NAME
        FROM   dual
        UNION ALL
        SELECT 'ABC_V_DEF4' VIEW_NAME
        FROM   dual) o;  

Answer 2

You can use an IN statement for this. I usually use an Excel formula to build the IN statement like, for example:

="'" & A1 & "', "

with A1 being the View Name if your Excel file.

That way it's easy to make the query:

select VIEW_NAME from ALL_VIEWS where VIEW_NAME IN ('ABC_V_DEF', 'NAME_2', 'NAME_3', 'ETC');

That will return only the views that are in your db from your list.

The second option is to create a temp table with all of your possible views from your Excel file. Then you can do:

SELECT T.VIEW_NAME, CASE WHEN AV.VIEW_NAME IS NULL THEN 'No' ELSE 'Yes' END "View Present?" FROM TEMP_TABLE T LEFT OUTER JOIN ALL_VIEWS AV ON T.VIEW_NAME = AV.VIEW_Name

Answer 3

Take your list of views, create a flat file and an EXTERNAL TABLE definition for the file and then run the following query;

SELECT evl.view_name,
       CASE WHEN av.view_name IS NULL THEN 'No' ELSE 'Yes' END AS "View Present?"
FROM   ext_table_views evl
       LEFT OUTER JOIN
       all_views av ON av.view_name = evl.view_name

The advantage of this is that you can have a list as long as you like and running with a new list simply involves replacing the file.

I guess that it really depends on how man view names you will be checking.