Trying to build a generic dynamic sql block

Question

Hi,
I have this requirement of wanting to compare column values in source and target( which are almost of the same structure) based on what table name is input by the user.
I came across a sql select statement developed by Tom kyte which kind of answers the question but what i am looking for is a more generic approach so that I can dynamically build a similar query and output very similar results.
Tom's example
So, using my assumptions and making your 'test case' (it isn't a test case yet, it is lacking) a better one:
ops$tkyte%ORA10GR2> create table t1(c1 number(2) primary key, c2 varchar2(10), c3
varchar2(10));
Table created.
ops$tkyte%ORA10GR2> create table t2(c1 number(2) primary key, c2 varchar2(10), c3
varchar2(10));
Table created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t1 values(1,'a','c');
1 row created.
ops$tkyte%ORA10GR2> insert into t2 values(1,'b','c');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t1 values(2,'a','b');
1 row created.
ops$tkyte%ORA10GR2> insert into t2 values(2,'a','c');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t1 values(3,'a','b');
1 row created.
ops$tkyte%ORA10GR2> insert into t2 values(3,'a','b');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t1 values(4,'a','b');
1 row created.
ops$tkyte%ORA10GR2> insert into t2 values(4,'x','y');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t1 values(5,'a','b');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2> insert into t2 values(6,'a','b');
1 row created.
ops$tkyte%ORA10GR2>
ops$tkyte%ORA10GR2>
select case sum(new_cnt - old_cnt) over(partition by c1)
when 1 then 'T2 (missing in T1)'
when -1 then 'T1 (missing in T2)'
else case old_cnt when 1 then 'T1' else 'T2' end
end "TABLE"
, C1 PK, C2, C3
, case when new_cnt = 1 and count(*) over(partition by c1) > 1 then (
case when lag(c2) over(partition by c1 order by new_cnt) = c2 then 0 else 1 end
+ case when lag(c3) over(partition by c1 order by new_cnt) = c3 then 0 else 2 end
) end COL_DIF_ID
from (
select c1, c2, c3, sum(old_cnt) old_cnt, sum(new_cnt) new_cnt from (
select o.*, 1 old_cnt, 0 new_cnt from t1 o
union all
select n.*, 0 old_cnt, 1 new_cnt from t2 n
) group by c1, c2, c3 having sum(old_cnt) <> sum(new_cnt)
) order by c1, new_cnt
TABLE PK C2 C3 COL_DIF_ID
T1 1 a c
T2 1 b c 1
T1 2 a b
T2 2 a c 2
T1 4 a b
T2 4 x y 3
T1 (missing in T2) 5 a b
T2 (missing in T1) 6 a b
It beautifully does the job but can we make this more generic in any manner using dynamic sql ?

Answer 1

Hi,
try this:
declare
cTable1 varchar2(30):='T1';
cTable2 varchar2(30):='T2';
cPK varchar2(30):='c1';
cSQL varchar2(4000):=null;
bFirst boolean:=true;
begin
cSQL:='select t1.*,t2.*,(case when t1.'||cPK||' is null then ''Missing in T1'' else null end) exists_t1,(case when t2.'||cPK||' is null then ''Missing in T2'' else null end) exists_t2,';
for c in(select column_name from
(select column_name from  user_tab_columns where table_name=cTable1 and column_name!=cPK
intersect
select column_name from  user_tab_columns where table_name=cTable2 and column_name!=cPK)) loop
if bFirst then
cSQL:=cSQL||'(case when';
bFirst:=false;
else
cSQL:=cSQL||' and ';
end if;
cSQL:=cSQL||'(t1.'||c.column_name||'=t2.'||c.column_name||' or (t1.'||c.column_name||' is null and t2.'||c.column_name||' is null))';
end loop;
cSQL:=cSQL||' then ''='' else ''!='' end) diff_t1_t2 from '||cTable1||' t1 full outer join '||cTable2||' t2 on(t1.'||cPK||'=t2.'||cPK||')';
dbms_output.put_line(cSQL);
end;then you can enclose the generated SQL with a select * from (..) where diff_t1_t2='!='
It will give you something like:
SELECT t1.*,
       t2.*,
       (CASE
           WHEN t1.c1 IS NULL THEN 'Missing in T1'
           ELSE NULL
        END) exists_t1,
       (CASE
           WHEN t2.c1 IS NULL THEN 'Missing in T2'
           ELSE NULL
        END) exists_t2,
       (CASE
           WHEN(   t1.C1 = t2.C1
                OR (    t1.C1 IS NULL
                    AND t2.C1 IS NULL))
        AND    (   t1.C2 = t2.C2
                OR (    t1.C2 IS NULL
                    AND t2.C2 IS NULL))
        AND    (   t1.C3 = t2.C3
                OR (    t1.C3 IS NULL
                    AND t2.C3 IS NULL)) THEN '='
           ELSE '!='
        END
       ) diff_t1_t2
FROM   T1 t1 FULL OUTER JOIN T2 t2 ON(t1.c1 = t2.c1)JV
Edited by: user11268895 on Jun 16, 2010 8:25 AM
Edited by: user11268895 on Jun 16, 2010 8:27 AM
Edited by: user11268895 on Jun 16, 2010 8:29 AM