How to display dummy values in oracle query [duplicate] - oracle

Question

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generate duplicate rows in Select statement in Oracle
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I have a student table in my oracle database with only two records for studentid 1002 for the month of march.
enter image description here
The two records are on date 14-Mar-11 and 20-Mar-11 as shown in the image.
I want to display dummy fake values on dates where their is no record in the table starting from 01-Mar-11 to 31-Mar-11.
My query should show dummy values and the actual values for this specific student and this specific month.
I need a SQL query for my oracle table to check row where their is no data and fill for each month as shown in the image.
enter image description here
My SQL query should show results for each student his old values and new values on row where their is no transaction.

Answer 1

Here's one option; it uses calendar for each student in source table, whose dates range from first day of the first month to the last day of the last month in date span. It is then outer joined to source table to produce final result.
Old/new value is fetched randomly.
Sample data:
SQL> with
2 student (studentid, datum, oldvalue, newvalue) as
3 (select 1112, date '2011-03-14', 50, 30 from dual union all
4 select 1112, date '2011-03-20', 30, 10 from dual union all
5 select 2345, date '2011-03-13', 10, 20 from dual
6 ),
Query begins here:
7 calendar (studentid, datum) as
8 (select studentid,
9 trunc(mindat, 'mm') + column_value - 1
10 from (select studentid,
11 min(datum) mindat,
12 max(datum) maxdat
13 from student
14 group by studentid
15 ) cross join table(cast(multiset
16 (select level from dual
17 connect by level <= last_day(maxdat) - trunc(mindat, 'mm') + 1
18 ) as sys.odcinumberlist))
19 )
20 select c.studentid,
21 c.datum,
22 nvl(s.oldvalue, round(dbms_random.value(1, 100))) oldvalue,
23 nvl(s.newvalue, round(dbms_random.value(1, 100))) newvalue
24 from calendar c left join student s on s.datum = c.datum
25 order by c.studentid, c.datum;
Result:
STUDENTID DATUM OLDVALUE NEWVALUE
---------- --------- ---------- ----------
1112 01-MAR-11 49 42
1112 02-MAR-11 21 26
1112 03-MAR-11 66 13
1112 04-MAR-11 72 73
1112 05-MAR-11 88 55
1112 06-MAR-11 36 32
1112 07-MAR-11 21 16
1112 08-MAR-11 98 53
1112 09-MAR-11 30 44
1112 10-MAR-11 15 77
1112 11-MAR-11 93 88
1112 12-MAR-11 65 45
1112 13-MAR-11 10 20 --> from source table
1112 14-MAR-11 50 30
1112 15-MAR-11 77 36
1112 16-MAR-11 78 85
1112 17-MAR-11 82 94
1112 18-MAR-11 22 32
1112 19-MAR-11 54 79
1112 20-MAR-11 30 10 --> from source table
1112 21-MAR-11 20 97
1112 22-MAR-11 11 98
1112 23-MAR-11 43 38
1112 24-MAR-11 68 86
1112 25-MAR-11 70 43
1112 26-MAR-11 98 35
1112 27-MAR-11 26 93
1112 28-MAR-11 56 27
1112 29-MAR-11 12 88
1112 30-MAR-11 78 43
1112 31-MAR-11 47 50
2345 01-MAR-11 59 70
2345 02-MAR-11 49 57
2345 03-MAR-11 63 75
2345 04-MAR-11 94 79
2345 05-MAR-11 2 49
2345 06-MAR-11 41 24
2345 07-MAR-11 75 36
2345 08-MAR-11 26 33
2345 09-MAR-11 31 48
2345 10-MAR-11 12 66
2345 11-MAR-11 88 3
2345 12-MAR-11 29 35
2345 13-MAR-11 10 20 --> from source table
2345 14-MAR-11 50 30
2345 15-MAR-11 75 2
2345 16-MAR-11 30 39
2345 17-MAR-11 19 68
2345 18-MAR-11 54 73
2345 19-MAR-11 73 37
2345 20-MAR-11 30 10
2345 21-MAR-11 35 10
2345 22-MAR-11 66 73
2345 23-MAR-11 71 52
2345 24-MAR-11 27 86
2345 25-MAR-11 73 22
2345 26-MAR-11 54 67
2345 27-MAR-11 46 75
2345 28-MAR-11 84 70
2345 29-MAR-11 63 31
2345 30-MAR-11 56 38
2345 31-MAR-11 76 24
62 rows selected.
SQL>