Display column values as zeros

Question

I am having three select queries with union below:
select col1, col2 from table1 where condition; -> fetches 1 record
union
select col1, col2 from table2 where condition; -> fetches no row
union
select col1, col2 from table3 where condition; -> fetches no row
so output is 1 row. example;
col1 col2
1 1
The 2nd and 3rd select doesnt fetch any record. My req is to dislplay the col values as zeros for any of 3 select statements which doesnt fetch any records from table
so req output which looks like:
col1 col2
1 1
0 0 -> norecords fetched(displaying zeros)
0 0 -> norecords fetched(displaying zeros)
Please let me know how can i do this in the query? I need to do this in the same qury and not using any functions/proc..
Edited by: user11942774 on Aug 22, 2010 4:13 AM

Answer 1

MichaelS wrote:
Or
SQL> var deptno1 number
SQL> var deptno2 number
SQL> begin
:deptno1 := 20;
:deptno2 := 100;
end;
PL/SQL procedure successfully completed.
SQL> select nvl (deptno, 0) deptno
from (select :deptno1 dn from dual), dept
where deptno(+) = dn
union all
select nvl (deptno, 0) deptno
from (select :deptno2 dn from dual), dept
where deptno(+) = dn
DEPTNO
20
0
2 rows selected.Note: Above worked on my old 9.8.0.2 but strange enough not on my 11.2.0.1 (Only the first part of the UNION ALL displayed)! A bug???Looks to be.
set serveroutput off
ALTER SESSION SET STATISTICS_LEVEL = ALL;
select nvl (deptno, 0) deptno
  from (select :deptno1 dn from dual), scott.dept
where deptno(+) = dn
union all
select nvl (deptno, 0) deptno
  from (select :deptno2 dn from dual), scott.dept
where deptno(+) = dn
  8  /
            DEPTNO
                20
1 row selected.
Elapsed: 00:00:00.01
TUBBY_TUBBZ?SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'ALL'));
PLAN_TABLE_OUTPUT
SQL_ID  ap0cr5cut2ucn, child number 0
select nvl (deptno, 0) deptno   from (select :deptno1 dn from dual),
scott.dept  where deptno(+) = dn union all select nvl (deptno, 0)
deptno   from (select :deptno2 dn from dual), scott.dept  where
deptno(+) = dn
Plan hash value: 18139613
| Id  | Operation            | Name               | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |                    |       |       |     2 (100)|          |
|   1 |  NESTED LOOPS OUTER  |                    |     2 |    26 |     2   (0)| 00:00:01 |
|   2 |   FAST DUAL          |                    |     1 |       |     2   (0)| 00:00:01 |
|   3 |   VIEW               | VW_JF_SET$03B38961 |     2 |    26 |     0   (0)|          |
|   4 |    UNION-ALL         |                    |       |       |            |          |
|*  5 |     INDEX UNIQUE SCAN| PK_DEPT            |     1 |     3 |     0   (0)|          |
|*  6 |     INDEX UNIQUE SCAN| PK_DEPT            |     1 |     3 |     0   (0)|          |
Query Block Name / Object Alias (identified by operation id):
   1 - SEL$51CD7FBE
   2 - SEL$51CD7FBE / DUAL@SEL$2
   3 - SET$03B38961 / VW_JF_SET$03B38961@SEL$7D8CA889
   4 - SET$03B38961
   5 - SEL$09480F13 / DEPT@SEL$1
   6 - SEL$05ED6B18 / DEPT@SEL$3
Predicate Information (identified by operation id):
   5 - access("DEPTNO"=:DEPTNO1)
   6 - access("DEPTNO"=:DEPTNO2)
Column Projection Information (identified by operation id):
   1 - "ITEM_1"[NUMBER,22]
   3 - "ITEM_1"[NUMBER,22]
   4 - STRDEF[22]
   5 - "DEPTNO"[NUMBER,22]
   6 - "DEPTNO"[NUMBER,22]
46 rows selected.
Elapsed: 00:00:00.05So we can see through rows 5 and 6 the predicates were pushed into DEPT query (which shouldn't have happened).
A simple change to the query alleviates the bug.
select
   nvl(d1.deptno, 0) as deptno
from
   select :deptno1 dn from dual
      union all
   select :deptno2 dn from dual
)  d,
   scott.dept d1
where
11     d.dn = d1.deptno (+)
12  /
            DEPTNO
                20
                 0
2 rows selected.
Elapsed: 00:00:00.01
TUBBY_TUBBZ?SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'ALL'));
PLAN_TABLE_OUTPUT
SQL_ID  4x59nkxusp1p8, child number 0
select    nvl(d1.deptno, 0) as deptno from (    select :deptno1 dn from
dual       union all    select :deptno2 dn from dual )  d,
scott.dept d1 where    d.dn = d1.deptno (+)
Plan hash value: 1564933512
| Id  | Operation          | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |         |       |       |     4 (100)|          |
|   1 |  NESTED LOOPS OUTER|         |     2 |    32 |     4   (0)| 00:00:01 |
|   2 |   VIEW             |         |     2 |    26 |     4   (0)| 00:00:01 |
|   3 |    UNION-ALL       |         |       |       |            |          |
|   4 |     FAST DUAL      |         |     1 |       |     2   (0)| 00:00:01 |
|   5 |     FAST DUAL      |         |     1 |       |     2   (0)| 00:00:01 |
|*  6 |   INDEX UNIQUE SCAN| PK_DEPT |     1 |     3 |     0   (0)|          |
Query Block Name / Object Alias (identified by operation id):
   1 - SEL$1
   2 - SET$1 / D@SEL$1
   3 - SET$1
   4 - SEL$2 / DUAL@SEL$2
   5 - SEL$3 / DUAL@SEL$3
   6 - SEL$1 / D1@SEL$1
Predicate Information (identified by operation id):
   6 - access("D"."DN"="D1"."DEPTNO")
Column Projection Information (identified by operation id):
   1 - "D1"."DEPTNO"[NUMBER,22]
   2 - "D"."DN"[NUMBER,22]
   3 - STRDEF[22]
   6 - "D1"."DEPTNO"[NUMBER,22]
43 rows selected.
Elapsed: 00:00:00.05
TUBBY_TUBBZ?I ran these tests on
TUBBY_TUBBZ?select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE     11.2.0.1.0     Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
5 rows selected.
Elapsed: 00:00:00.02
TUBBY_TUBBZ?