Issue in my Dynamic Query - postgresql

Question

select * from pg_tables where schemaname ='reports' and tablename like '%enhancedreports03_0%' order by tablename;
schemaname | tablename | tableowner |
tablespace | hasindexes | hasrules | hastriggers
------------+--------------------------------+---------------------+--------------+------------+----------+------------- reports | enhancedreports03_0_1970_01_01 | ss_agent_summarizer |
rpt_data_tbs | t | f | f reports |
enhancedreports03_0_2013_10_08 | ss_agent_summarizer | rpt_data_tbs |
t | f | f
Check constraints:
"enhancedreports03_0_1970_01_01_check" CHECK (0::double precision >= date_part('epoch'::text, '1970-01-01'::date) AND 0::double precision < date_part('epoch'::text, '1970-01-02'::date))
I need to drop the constraints in both the tables..So i tried an dynamic query to generate the result set...
select 'ALTER TABLE '||schemaname ||'.'||tablename||' DROP CONSTRAINT '||conname||'' from pg_tables a, pg_constraint b
where schemaname ='reports' and tablename like '%enhancedreports03_0%' and conname like '%enhancedreports03_0_%' order by tablename;
?column?
ALTER TABLE reports.enhancedreports03_0_1970_01_01 DROP CONSTRAINT
enhancedreports03_0_1970_01_01_check ALTER TABLE
reports.enhancedreports03_0_1970_01_01 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check ALTER TABLE
reports.enhancedreports03_0_1970_01_01 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check ALTER TABLE
reports.enhancedreports03_0_1970_01_01 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check ALTER TABLE
reports.enhancedreports03_0_2013_10_08 DROP CONSTRAINT
enhancedreports03_0_1970_01_01_check ALTER TABLE
reports.enhancedreports03_0_2013_10_08 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check ALTER TABLE
reports.enhancedreports03_0_2013_10_08 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check ALTER TABLE
reports.enhancedreports03_0_2013_10_08 DROP CONSTRAINT
enhancedreports03_0_2013_10_08_check
(8 rows)
I need the result set to be like this
ALTER TABLE reports.enhancedreports03_0_1970_01_01 DROP CONSTRAINT enhancedreports03_0_1970_01_01_check
ALTER TABLE reports.enhancedreports03_0_2013_10_08 DROP CONSTRAINT enhancedreports03_0_2013_10_08_check
Thanks in advance
Abdul

Answer 1

Try to query information_schema.table_constraints where you can query for table directly instead:
select
*
from
information_schema.table_constraints
where
table_name like 'enhancedreports03_0_%%'
order by
table_name;
The problem with your query is that you are creating cross join because of missing join between pg_tables and pg_constraint.
Easiest would be to use:
select
'ALTER TABLE '||table_schema ||'.'||table_name||
' DROP CONSTRAINT '||constraint_name||';'
from
information_schema.table_constraints
where
table_schema ='reports'
and table_name like '%enhancedreports03_0%'
and constraint_name like '%enhancedreports03_0_%'
order by
table_name;
Documentation
If you would like to use pg catalog, then you have to join tables properly:
select
relname,
conname
from
pg_class pcl
join pg_constraint pco on (pcl.oid = pco.conrelid)
where
relname like 'enhancedreports03_0_%'

Answer 2

I have check your code in my system it worked absolutely fine and give out put u want so i have add one ; at the end hope this will help you.
select 'ALTER TABLE '||schemaname ||'.'||tablename||' DROP CONSTRAINT '||conname||';' from pg_tables a, pg_constraint b
where schemaname ='reports' and tablename like '%enhancedreports03_0%' and conname like '%enhancedreports03_0_%' order by tablename;