Find exactly equal rows in 2 tables, both in terms of value and number - sql

Question

I have two Table, that both of them have 2 field (provinceid,cityid)
i want to find provinceid that have exactly the same cityid in this two table.
for example i have this tables:
table1:
provinceid
cityid
1
1
1
2
2
3
2
4
3
6
table2:
provinceid
cityid
1
1
1
5
2
3
2
4
3
6
3
7
i want a query that just return provinceid =2 and city id =3 and 4.
i try this query and it is right. but i want a better query:
select provinceid ,t1.cityid
from t1
left join t2 on t1=provinceid=t2.provinceid and t1.cityid=t2.cityid
where t2.provinceid is not null and t2.cityid is not null
and t1.provinceid not in (select provinceid
from t2
left join t1 on t1=provinceid=t2.provinceid and t1.cityid=t2.cityid
where t1.provinceid is not null and t1.cityid is not null)
thank you

Answer 1

Try this :
select t1.provinceid ,t1.cityid
from table1 t1 join table2 t2
on t1.provinceid=t2.provinceid
and t1.cityid=t2.cityid
and t1.provinceid in (
select distinct(t1.provinceid)
from
(select provinceid, count(provinceid) as cnt from table1 group by provinceid) as t1
cross join
(select provinceid ,count(provinceid) as cnt from table2 group by provinceid) as t2
where t1.cnt = t2.cnt);
Output:
provinceid
cityid
1
1
2
3
2
4

Answer 2

The simplest method for an exact match is to use string aggregation. The exact syntax varies by database, but in Standard SQL this looks like:
select t1.provinceid, t2.provinceid
from (select provinceid,
listagg(cityid, ',') within group (order by cityid) as cities
from t1
group by provinceid
) t1 join
(select provinceid,
listagg(cityid, ',') within group (order by cityid) as cities
from t2
group by provinceid
) t2
on t1.cities = t2.cities;
If you want the provinceids to be the same as well, just add t1.provinceid = t2.provinceid to the on clause.
Or, if you want the provinceids to be the same, you can use full join instead:
select provinceid
from t1 full join
t2
using (provinceid, cityid)
group by provinceid
having count(*) = count(t1.cityid) and count(*) = count(t2.cityid);

Answer 3

Besides match in provid and cityid, we are looking for exactly matching sets of records as well. There might be many different methods to this. I prefer to have string comparison for list of cities for each provide with addition to provide and cityid match clause to remove other sets of provide and cityid which are available in tables but not the exact row match.
WITH table1 AS(
SELECT 1 AS PROVID, 1 AS CITYID FROM DUAL UNION ALL
SELECT 1 AS PROVID, 2 AS CITYID FROM DUAL UNION ALL
SELECT 2 AS PROVID, 3 AS CITYID FROM DUAL UNION ALL
SELECT 2 AS PROVID, 4 AS CITYID FROM DUAL UNION ALL
SELECT 3 AS PROVID, 6 AS CITYID FROM DUAL
),
table2 AS (
SELECT 1 AS PROVID, 1 AS CITYID FROM DUAL UNION ALL
SELECT 1 AS PROVID, 5 AS CITYID FROM DUAL UNION ALL
SELECT 2 AS PROVID, 3 AS CITYID FROM DUAL UNION ALL
SELECT 2 AS PROVID, 4 AS CITYID FROM DUAL UNION ALL
SELECT 3 AS PROVID, 6 AS CITYID FROM DUAL UNION ALL
SELECT 3 AS PROVID, 7 AS CITYID FROM DUAL
),
listed_table1 AS (
SELECT
a.provid,
listagg(cityid,',') within GROUP (ORDER BY cityid) list_city
FROM table1 a
GROUP BY a.provid
),
listed_table2 AS (
SELECT
a.provid,
listagg(cityid,',') within GROUP (ORDER BY cityid) list_city
FROM table2 a
GROUP BY a.provid
)
SELECT
t1.provid, t1.cityid
FROM
(SELECT x.*, x1.list_city FROM table1 x, listed_table1 x1 WHERE x.provid = x1.provid) t1,
(SELECT y.*, y1.list_city FROM table2 y, listed_table2 y1 WHERE y.provid = y1.provid) t2
WHERE t1.provid = t2.provid AND t1.cityid = t2.cityid AND t1.list_city = t2.list_city
;

Answer 4

You can use (union ..)except (inner join..) to detect non-matches. Step by step
with u12 as (
select PROVID, CITYID from table1
union
select PROVID, CITYID from table2
),
c12 as (
select t1.PROVID, t2.CITYID
from table1 t1
join table2 t2 on t1.PROVID=t2.PROVID and t1.CITYID=t2.CITYID
),
nonMatch as (
select distinct PROVID
from (
select PROVID, CITYID from u12
except
select PROVID, CITYID from c12
) t
)
select *
from table1 t
where not exists (
select 1
from nonMatch n
where n.PROVID = t.PROVID);
If a number of doubles counts then count them first
with t1 as (
select PROVID, CITYID, count(*) n
from table1
group by PROVID, CITYID
),
t2 as (
select PROVID, CITYID, count(*) n
from table2
group by PROVID, CITYID
),
u12 as (
select PROVID, CITYID, n from t1
union
select PROVID, CITYID, n from t2
),
c12 as (
select t1.PROVID, t1.CITYID, t1.n
from t1
join t2 on t1.PROVID = t2.PROVID and t1.CITYID = t2.CITYID and t1.n = t2.n
),
nonMatch as (
select distinct PROVID
from (
select PROVID, CITYID, n from u12
except
select PROVID, CITYID, n from c12
) t
)
select *
from table1 t
where not exists (
select 1
from nonMatch n
where n.PROVID = t.PROVID)
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