Find data by multiple Lookup table clauses - sql

Question

declare #Character table (id int, [name] varchar(12));
insert into #Character (id, [name])
values
(1, 'tom'),
(2, 'jerry'),
(3, 'dog');
declare #NameToCharacter table (id int, nameId int, characterId int);
insert into #NameToCharacter (id, nameId, characterId)
values
(1, 1, 1),
(2, 1, 3),
(3, 1, 2),
(4, 2, 1);
The Name Table has more than just 1,2,3 and the list to parse on is dynamic
NameTable
id | name
----------
1 foo
2 bar
3 steak
CharacterTable
id | name
---------
1 tom
2 jerry
3 dog
NameToCharacterTable
id | nameId | characterId
1 1 1
2 1 3
3 1 2
4 2 1
I am looking for a query that will return a character that has two names. For example
With the above data only "tom" will be returned.
SELECT *
FROM nameToCharacterTable
WHERE nameId in (1,2)
The in clause will return every row that has a 1 or a 3. I want to only return the rows that have both a 1 and a 3.
I am stumped I have tried everything I know and do not want to resort to dynamic SQL. Any help would be great
The 1,3 in this example will be a dynamic list of integers. for example it could be 1,3,4,5,.....

Answer 1

Filter out a count of how many times the Character appears in the CharacterToName table matching the list you are providing (which I have assumed you can convert into a table variable or temp table) e.g.
declare #Character table (id int, [name] varchar(12));
insert into #Character (id, [name])
values
(1, 'tom'),
(2, 'jerry'),
(3, 'dog');
declare #NameToCharacter table (id int, nameId int, characterId int);
insert into #NameToCharacter (id, nameId, characterId)
values
(1, 1, 1),
(2, 1, 3),
(3, 1, 2),
(4, 2, 1);
declare #RequiredNames table (nameId int);
insert into #RequiredNames (nameId)
values
(1),
(2);
select *
from #Character C
where (
select count(*)
from #NameToCharacter NC
where NC.characterId = c.id
and NC.nameId in (select nameId from #RequiredNames)
) = 2;
Returns:
id
name
1
tom
Note: Providing DDL+DML as shown here makes it much easier for people to assist you.

Answer 2

This is classic Relational Division With Remainder.
There are a number of different solutions. #DaleK has given you an excellent one: inner-join everything, then check that each set has the right amount. This is normally the fastest solution.
If you want to ensure it works with a dynamic amount of rows, just change the last line to
) = (SELECT COUNT(*) FROM #RequiredNames);
Two other common solutions exist.
Left-join and check that all rows were joined
SELECT *
FROM #Character c
WHERE EXISTS (SELECT 1
FROM #RequiredNames rn
LEFT JOIN #NameToCharacter nc ON nc.nameId = rn.nameId AND nc.characterId = c.id
HAVING COUNT(*) = COUNT(nc.nameId) -- all rows are joined
);
Double anti-join, in other words: there are no "required" that are "not in the set"
SELECT *
FROM #Character c
WHERE NOT EXISTS (SELECT 1
FROM #RequiredNames rn
WHERE NOT EXISTS (SELECT 1
FROM #NameToCharacter nc
WHERE nc.nameId = rn.nameId AND nc.characterId = c.id
)
);
A variation on the one from the other answer uses a windowed aggregate instead of a subquery. I don't think this is performant, but it may have uses in certain cases.
SELECT *
FROM #Character c
WHERE EXISTS (SELECT 1
FROM (
SELECT *, COUNT(*) OVER () AS cnt
FROM #RequiredNames
) rn
JOIN #NameToCharacter nc ON nc.nameId = rn.nameId AND nc.characterId = c.id
HAVING COUNT(*) = MIN(rn.cnt)
);
db<>fiddle