How to select an entry without specific entries? - mysql

Question

I have two SQL-tables like this:
T1
Animal Name
Cat Paul
Cat Miau
Cat Paul
Cat Peter
T2
Legs Name
4 Paul
4 Miau
3 Paul
4 Peter
What I want to have is a table like this:
Animal Legs Name
Cat 4 Miau
Cat 4 Peter
I want to have all animals with a specific number of legs but not when we have two cats with the same name.
I tried doing something like these:
select a.animal, b.legs, a.name
from animallistA as a join animallistB as b
on a.name = b.name
where b.legs = 4 and not b.legs = 3
group by a.animal, b.legs, a.name
If I say where b.legs = 4 then I'll also receive 'Paul' but If I say where b.legs = 4 and not b.legs = 3 I receive nothing at all.
Is there a way not to receive the cats who have the same name and 4 legs but not the one that have the same name but either 4 or less(or more) legs.

Answer 1

NOT EXISTS may do the job.
SELECT t1.animal, t2.legs, t2.name
FROM t1
JOIN t2 ON t1.name = t2.name
WHERE t2.legs = 4 AND
NOT EXISTS
(
SELECT 1 FROM t2 WHERE t2.name = t1.name AND t2.legs != 4
)

Answer 2

You can first take all the unique names of 4 legs animals ( from subquery ) and then join with the main table to get required result.
select a.animal, b.legs, a.name from animallistA as a join
(select name,max(legs) legs from animallistB group by name having count(distinct legs)=1) as b
on a.name = b.name and b.legs=4
From subquery we can get result
Legs Name
4 Miau
4 Peter
Because distinct values in having condition fail for Paul. Joining this with main table gives the requested result

Answer 3

AS far as I understood your question I suggest following query:
SELECT A.ANIMAL, A.NAME, B.LEGS
FROM ANIMALLISTA A
INNER JOIN ANIMALLISTB B ON A.NAME = B.NAME
LEFT JOIN (SELECT NAME, COUNT(*) AS RC FROM ANIMALLISTB GROUP BY NAME) C ON A.NAME = C.NAME
WHERE B.LEGS=4
AND C.RC=1
Output:
ANIMAL NAME LEGS
Cat Miau 4
Cat Peter 4

Answer 4

You might wanna try something like this, worked for me on My SQL 8.0.2
|| cat_1 = T1 and cat_2 = T2
WITH CTE AS
(
SELECT distinct *
FROM cat_1
INNER JOIN cat_2 ON cat_1.names=cat_2.name
),
SCTE AS
(
SELECT CTE.animal,
CTE.legs,
CTE.names,
COUNT(CTE.names) over(PARTITION BY CTE.names) as Count
from CTE
)
SELECT
SCTE.animal,
SCTE.legs,
SCTE.names
FROM SCTE
WHERE legs = 4
AND Count = 1;
Output:
animal legs names
Cat 4 Miau
Cat 4 Peter