Unable to understand Connect by with this SQL

Question

I have to generate a sequence like this for a record based on the count. For eg., E1 has a value 4, then the SQL below
with tmp as
select 'E1' as emp, 4 as cnt from dual
SELECT emp, LEVEL rn
FROM tmp
CONNECT BY LEVEL < cnt + 1 ;
produces 4 records
E1,1
E2,1
E3,1
E4,1
But, when I have another record E2 also as shown below
with tmp as
select 'E1' as emp, 4 as cnt from dual
union
select 'E2' as emp, 4 as cnt from dual
SELECT emp, LEVEL rn
FROM tmp
CONNECT BY LEVEL < cnt + 1 ;
it produces 30 records. I was expecting only 8. I had to put a distinct to avoid it. So, can I generate 4 for each E1,E2 without using distinct.
The actual table that I have is a huge table and so trying to avoid distinct. Thanks.
Satish

Answer 1

Hi, Satish,
user572405 wrote:
I have to generate a sequence like this for a record based on the count. For eg., E1 has a value 4, then the SQL below
with tmp as
select 'E1' as emp, 4 as cnt from dual
SELECT emp, LEVEL rn
FROM tmp
CONNECT BY LEVEL < cnt + 1 ;
produces 4 records
E1,1
E2,1
E3,1
E4,1Really?
When I run that, I get this output:
EM         RN
E1          1
E1          2
E1          3
E1          4
But, when I have another record E2 also as shown below
with tmp as
select 'E1' as emp, 4 as cnt from dual
union
select 'E2' as emp, 4 as cnt from dual
SELECT emp, LEVEL rn
FROM tmp
CONNECT BY LEVEL < cnt + 1 ;
it produces 30 records. I was expecting only 8. I had to put a distinct to avoid it. So, can I generate 4 for each E1,E2 without using distinct.
The actual table that I have is a huge table and so trying to avoid distinct. Thanks."CONNECT BY LEVEL < x" (with no other conditions) should only be used on one-row tables, like dual.
Perhaps you need to join such a result set to another table (or result set), like this:
WITH     emps     AS
     SELECT     'E1' AS emp,     4 AS cnt     FROM dual
     UNION ALL
     SELECT     'E2' AS emp,     4 AS cnt     FROM dual
,     cntr     AS
     SELECT     LEVEL     AS rn
     FROM     dual
     CONNECT BY     LEVEL     <=
               SELECT     MAX (cnt)
               FROM     emps
SELECT     emp
,     rn
FROM     emps
JOIN     cntr     ON     cntr.rn     <= emps.cnt
;which produces:
EM         RN
E1          1
E2          1
E1          2
E2          2
E1          3
E2          3
E1          4
E2          4Edited by: Frank Kulash on Dec 31, 2008 3:44 PM