Question

I have (2) case statements:

SELECT CASE WHEN EXISTS
                   ( SELECT *
                     FROM MYTABLE_A
                     WHERE timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
                   )
            THEN 0
            ELSE 1
       END AS FLAG_MYTABLE_A
from DUAL;
SELECT CASE WHEN EXISTS
                   ( SELECT *, timestamp
                     FROM MYTABLE_B
                     WHERE
                     timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
                   )                       )
            THEN 0
            ELSE 1
       END AS FLAG_MYTABLE_B
from DUAL;

RESULTS:

FLAG_MYTABLE_A
--------------
             0

FLAG_MYTABLE_B
--------------
         1

I need help constructing this query so I can get the following results displayed.

MYTABLENAME       MYFLAG
-----------       ------
MYTABLE_A              0
MYTABLE_B              1

Am I looking at a nested select? Can someone show me how to set this up?

Answer 1

You can use UNION ALL:

SELECT 'MYTABLE_A' AS MYTABLENAME, CASE WHEN EXISTS
                   ( SELECT *
                     FROM MYTABLE_A
                     WHERE timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
                   )
            THEN 0
            ELSE 1
       END AS FLAG_MYTABLE_A
from DUAL
UNION ALL
SELECT 'MYTABLE_B' AS MYTABLENAME, CASE WHEN EXISTS
                   ( SELECT *, timestamp
                     FROM MYTABLE_B
                     WHERE
                     timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
                   )                       )
            THEN 0
            ELSE 1
       END AS FLAG_MYTABLE_B
from DUAL;