How to compare two identicals tables data of each column in postgres? - postgresql

Question

I want compare two table's all column values.The two table is identical tables means column number is same and primary key is same. can any one suggest query which compare such two tables in postgres.
The query should give the column name and what is the two different value of two tables.Like this
pkey | column_name | table1_value | table2_value
123 | bonus | 1 | 0

Answer 1

To get all different rows you can use:
select *
from table_1 t1
join table_2 t2 on t1.pkey = t2.pkey
where t1 is distinct from t2;
This will only compare rows that exist in both tables. If you also want to find those that are missing in on of them use a full outer join:
select coalesce(t1.pkey, t2.pkey) as pkey,
case
when t1.pkey is null then 'Missing in table_1'
when t2.pkey is null then 'Missing in table_2'
else 'At least one column is different'
end as status,
*
from table_1 t1
full ojoin table_2 t2 on t1.pkey = t2.pkey
where (t1 is distinct from t2)
or (t1.pkey is null)
or (t2.pkey is null);
If you install the hstore extension, you can view the differences as a key/value map:
select coalesce(t1.pkey, t2.pkey) as pkey,
case
when t1.pkey is null then 'Missing in table_1'
when t2.pkey is null then 'Missing in table_2'
else 'At least one column is different'
end as status,
hstore(t1) - hstore(t2) as values_in_table_1,
hstore(t2) - hstore(t1) as values_in_table_2
from table_1 t1
full ojoin table_2 t2 on t1.pkey = t2.pkey
where (t1 is distinct from t2)
or (t1.pkey is null)
or (t2.pkey is null);
Using this sample data:
create table table_1 (pkey integer primary key, col_1 text, col_2 int);
insert into table_1 (pkey, col_1, col_2)
values (1, 'a', 1), (2, 'b', 2), (3, 'c', 3), (5, 'e', 42);
create table table_2 (pkey integer primary key, col_1 text, col_2 int);
insert into table_2 (pkey, col_1, col_2)
values (1,'a', 1), (2, 'x', 2), (3, 'c', 33), (4, 'd', 52);
A possible result would be:
pkey | status | values_in_table_1 | values_in_table_2
-----+----------------------------------+-------------------+------------------
2 | At least one column is different | "col_1"=>"b" | "col_1"=>"x"
3 | At least one column is different | "col_2"=>"3" | "col_2"=>"33"
4 | Missing in table_1 | |
5 | Missing in table_2 | |

Answer 2

Example data:
create table test1(pkey serial primary key, str text, val int);
insert into test1 (str, val) values ('a', 1), ('b', 2), ('c', 3);
create table test2(pkey serial primary key, str text, val int);
insert into test2 (str, val) values ('a', 1), ('x', 2), ('c', 33);
This simple query gives a complete information on differences of two tables (including rows missing in one of them):
(select 1 t, * from test1
except
select 1 t, * from test2)
union all
(select 2 t, * from test2
except
select 2 t, * from test1)
order by pkey, t;
t | pkey | str | val
---+------+-----+-----
1 | 2 | b | 2
2 | 2 | x | 2
1 | 3 | c | 3
2 | 3 | c | 33
(4 rows)
In Postgres 9.5+ you can transpose the result to the expected format using jsonb functions:
select pkey, key as column, val[1] as value_1, val[2] as value_2
from (
select pkey, key, array_agg(value order by t) val
from (
select t, pkey, key, value
from (
(select 1 t, * from test1
except
select 1 t, * from test2)
union all
(select 2 t, * from test2
except
select 2 t, * from test1)
) s,
lateral jsonb_each_text(to_jsonb(s))
group by 1, 2, 3, 4
) s
group by 1, 2
) s
where key <> 't' and val[1] <> val[2]
order by pkey;
pkey | column | value_1 | value_2
------+--------+---------+---------
2 | str | b | x
3 | val | 3 | 33
(2 rows)

Answer 3

I tried all of the above answer.Thanks guys for your help.Bot after googling I found a simple query.
SELECT <common_column_list> from table1
EXCEPT
SELECT <common_column_list> from table2.
It shows all the row of table1 if any table1 column value is different from table2 column value.

Answer 4

Not very nice but fun and it works :o)
Just replace public.mytable1 and public.mytable2 by correct tables and
update the " where table_schema='public' and table_name='mytable1'"
select * from (
select pkey,column_name,t1.col_value table1_value,t2.col_value table2_value from (
select pkey,generate_subscripts(t,1) ordinal_position,unnest(t) col_value from (
select pkey,
(
replace(regexp_replace( -- null fields
'{'||substring(a::character varying,'^.(.*).$') ||'}' -- {} instead of ()
,'([\{,])([,\}])','\1null\2','g'),',,',',null,')
)::TEXT[] t
from public.mytable1 a
) a) t1
left join (
select pkey,generate_subscripts(t,1) ordinal_position,unnest(t) col_value from (
select pkey,
(
replace(regexp_replace( -- null fields
'{'||substring(a::character varying,'^.(.*).$') ||'}' -- {} instead of ()
,'([\{,])([,\}])','\1null\2','g'),',,',',null,')
)::TEXT[] t
from public.mytable2 a
) a) t2 using (pkey,ordinal_position)
join (select * from information_schema.columns where table_schema='public' and table_name='mytable1') c using (ordinal_position)
) final where COALESCE(table1_value,'')!=COALESCE(table2_value,'')