When to add joins to a query - sql

Question

Background
We have a bunch of Java code which generates an SQL query. When generating the conditions for the WHERE part, we are having some difficulties inducing the necessary joins.
The purpose of the query is always to return the zoo's id (see Database Structure).
Database Structure
Context
In the UI the user defines separately the filtering logic and the WHERE clause pieces. An example
Filtering logic: "1 OR (2 AND 3) OR (4 AND 5)"
WHERE clause pieces:
1: animal.name = "jack"
2: zoo.city = "Los Angeles"
3: animal.species = "bear"
4: animal.species = "fish"
5: animal.name = "henrietta"
Problem
The problem is that depending on the filtering logic and the WHERE clause pieces, extra joins might be necessary. At the very least new join is required when you have a query with like "(species = A AND name = B) AND (species = C AND name = D)" (both species and name columns are compared to different values while being in AND relation). Note that this query only makes sense because it is suppose to return the zoo's id where all of these conditions are true.
So my problem is that I do not know how many joins are absolutely necessary. I don't know the logic with which I will arrive at the answer. Because an extra join is not necessary if you have a query like "(species = A OR species = B)".
Expected Behavior
The following query should return the IDs of all zoos where there are two animals with names jack and tanya.
SELECT zoo.id FROM zoo
INNER JOIN animal a1 ON zoo.id = a1.zoo_id
INNER JOIN animal a2 ON zoo.id = a2.zoo_id
WHERE
a1.name = "jack"
AND a2.name = "tanya";
This query illustrates the need for two joins. The next one illustrates the case where only one join is sufficient.
SELECT zoo.id FROM zoo
INNER JOIN animal ON zoo.id = animal.zoo_id
WHERE
animal.name = "jack"
OR animal.name = "tanya";
Naive Solution
The simplest possible solution is to add one join for each animal table reference but there are serious performance consequences; increase of thousands of percents when compared to minimal joins.

Answer 1

This baseline for any query of what you have would be as follows...
SELECT
a.species,
a.name,
z.city
from
animals a
join zoo z
ON a.zoo_id = z.id
Then, just add your query criteria into the WHERE clause, such as
where
( a.name = 'jack' )
OR ( a.species = 'bear' AND z.city = 'Los Angeles' )
OR ( a.species = 'fish' AND a.name = 'henrietta' )
It goes through all the animals entries ONCE and pulls out those that qualify. I would also have an index on animals by (species, name), and the zoo table indexed on (id, city)

Answer 2

You don't need extra joins.
Just join on the Zoo ID and you can add to the end of your statement "WHERE...."
EDIT: Are you doing "JOIN ON" ? If so, take the filter out of the join and just put it at the end.