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# Virtual partitioning

## If you want to divide a table into an equal number of partitions by rowid range then you can use this SQL.

If you want to divide a table into an equal number of partitions by rowid range then you can use the following...

SQL. Just replace the with the actual table and run. When asked for input, enter the number of rows you want in each partition.

```
1 select
2  (CASE WHEN (
3     case when rnum = 1 OR mod(rnum,&&PART)= 1 then ceil(rnum/&&PART) end)
4          IS NOT NULL AND
5            (case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
6                    ceil(rnum/&&PART) end) IS NOT NULL
7       THEN
8            (NVL((case when rnum = 1 OR mod(rnum,&&PART)= 1 then
9                                  ceil(rnum/&&PART) end),0) +
10             NVL((case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
11                              ceil(rnum/&&PART) end),0))/2
12       ELSE
13            (NVL((case when rnum = 1 OR mod(rnum,&&PART)= 1 then
14                                  ceil(rnum/&&PART) end),0) +
15            NVL((case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
16                              ceil(rnum/&&PART) end),0))
17       END) seq
18  ,MAX((case when rnum = 1 OR mod(rnum,&&PART)= 1 THEN b.rid end)) lrowid
19  ,MAX((CASE WHEN mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0
20                    THEN b.rid end)) hrowid
21  ,MAX((case when rnum = 1 OR mod(rnum,&&PART)= 1 THEN b.rnum end)) lrnum
22  ,MAX((CASE WHEN mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0
23                    THEN b.rnum end)) hrnum
24  ,(MAX((CASE WHEN mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0
25                    THEN b.rnum end))
26  -MAX((case when rnum = 1 OR mod(rnum,&&PART)= 1 THEN b.rnum end))+1) recnum
27  from (
28  select rid,total,rnum from
29  (
30  select rowid rid
31  ,count(rowid) over () total
32  ,row_number() over (order by rowid) rnum
33  from <TABLE_NAME>
34  ) )b
35  where b.rnum IN (1,total
36  ,case when mod(rnum,&&PART) = 0 OR mod(rnum-1,&&PART) = 0 then rnum end)
37  group by
38      (CASE WHEN (
39        case when rnum = 1 OR mod(rnum,&&PART)= 1 then ceil(rnum/&&PART) end)
40                    IS NOT NULL AND
41                (case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
42                                     ceil(rnum/&&PART) end) IS NOT NULL THEN
43       ( NVL((case when rnum = 1 OR mod(rnum,&&PART)= 1 then
44                                  ceil(rnum/&&PART) end),0) +
45         NVL((case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
46                              ceil(rnum/&&PART) end),0))/2
47       ELSE
48       ( NVL((case when rnum = 1 OR mod(rnum,&&PART)= 1 then
49                                  ceil(rnum/&&PART) end),0) +
50         NVL((case when mod(rnum,&&PART)= 0 OR mod(rnum,total) = 0 then
51                              ceil(rnum/&&PART) end),0))
52       END)
53  /
```

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This was last published in December 2001

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