Oracle - 即时加入内联表或表

Question

I have a problem where a validation Code is stored in my table along with other data. Unfortunately the description is stored in a table where I dont have access to. I do know the values

Example

12, 14, and 22- Description for them is available in an excel. I have no permissions to create a table to store the data and I need to run them every day as a reporting work.

• 12- Missing Work
• 14 - Absent
• 22 - Incomplete

Question: how do I write a query where I can create a dummy table(inline? On the fly?) with the values in excel and join to my table so that results looks like this

Note:

• I cant create a perm table - no permissions. Its a read only Db for me
• I want to give 12,MissingWork, 14, Absent as part of my query

Any thoughts. I tried searching. I think I am not using the right terminology and hence not finding results.

Answer 1

You can do that by joining a subquery that SELECT s each code description pair FROM dual and uses UNION ALL to combine their results into one set.

SELECT t1.date,
       t1.task,
       t1.code,
       x.description
       FROM table1 t1
            LEFT JOIN (SELECT 12 code,
                              'Missing Work' description
                              FROM dual
                       UNION ALL
                       SELECT 14 code,
                              'Absent' description
                              FROM dual
                       ...) x
                      ON x.code = t1.code;

Answer 2

As you know those codes and descriptions, a simple option is to create a CTE; in the following example, it is called excel . Another CTE in this example represents your "real" table1 (I could have created it in my database, but CTE is good enough to show what to do).

SQL> with excel (code, description) as
  2    (select 12, 'Missing Work' from dual union all
  3     select 14, 'Absent'       from dual union all
  4     select 22, 'Incomplete'   from dual
  5    ),
  6    table1 (c_date, task, code) as
  7    (select date '2019-05-30', 'Homework', 12 from dual union all
  8     select date '2019-05-31', 'Labwork' , 14 from dual union all
  9     select date '2019-05-30', 'Other'   , 22 from dual
 10    )
 11  select t.c_date, t.task, t.code, e.description
 12  from table1 t join excel e on e.code = t.code;

C_DATE     TASK           CODE DESCRIPTION
---------- -------- ---------- ------------
05/30/2019 Homework         12 Missing Work
05/31/2019 Labwork          14 Absent
05/30/2019 Other            22 Incomplete

SQL>

Answer 3

You can use something called Common Table Expressions (CTE)

WITH Code_lookup AS (
  SELECT 12 Code, 'Missing Work' Description FROM DUAL UNION ALL
  SELECT 14, 'Absent' FROM DUAL UNION ALL
  SELECT 22, 'Incomplete' FROM DUAL)
SELECT <your columns list>
  FROM <your table>
  JOIN Code_lookup USING (Code)

Answer 4

Perhaps use a common table expression with a union:

with descr (code, description) as (
    select 12, 'Missing Work' from dual union
    select 14, 'Absent' from dual union
    select 22, 'Incomplete' from dual
)
select table1.date, table1.task, table1.code, descr.description
from table1
left join descr on table1.code = descr.code

Answer 5

In Oracle there is a DECODE function that would be suitable.

select code,
       DECODE(code, 12, 'Missing work',
                    14, 'Absent'
                    22, 'Incomplete',
                    'UNKNOWN Code) as Description
from table;

The first argument is the field to decode, followed by pairs of values for the mapping, and a final value which is the decoded value when there is no match. You code use a CTE and distinct to turn it into a proper table if that's what's needed. Then you would have the decode in a single place and wouldn't have to inline it everywhere.