Matching delimited string to table rows - sql

Question

So I have two tables in this simplified example: People and Houses. People can own multiple houses, so I have a People.Houses field which is a string with comma delimeters (eg: "House1, House2, House4"). Houses can have multiple people in them, so I have a Houses.People field, which works the same way ("Sam, Samantha, Daren").
I want to find all the rows in the People table corresponding to the the names of people in the given house, and vice versa for houses belong to people. But I can't figure out how to do that.
This is as close as I've come up with so far:
SELECT People.*
FROM Houses
LEFT JOIN People ON Houses.People Like CONCAT(CONCAT('%', People.Name), '%')
WHERE House.Name = 'SomeArbitraryHouseImInterestedIn'
But I get some false positives (eg: Sam and Samantha might both get grabbed when I just want Samantha. And likewise with House3, House34, and House343, when I want House343).
I thought I might try and write a SplitString function so I could split a string (using a list of delimiters) into a set, and do some subquery on that set, but MySQL functions can't have tables as return values.
Likewise you can't store arrays as fields, and from what I gather the comma-delimited elements in a long string seems to be the usual way to approach this problem.
I can think of some different ways to get what I want but I'm wondering if there isn't a nice solution.

Answer 1

Likewise you can't store arrays as fields, and from what I gather the comma-delimited elements in a long string seems to be the usual way to approach this problem.
I hope that's not true. Representing "arrays" in SQL databases shouldn't be in a comma-delimited format, but the problem can be correctly solved by using a junction table. Comma-separated fields should have no place in relational databases, and they actually violates the very first normal form.
You'd want your table schema to look something like this:
CREATE TABLE people (
id int NOT NULL,
name varchar(50),
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE houses (
id int NOT NULL,
name varchar(50),
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE people_houses (
house_id int,
person_id int,
PRIMARY KEY (house_id, person_id),
FOREIGN KEY (house_id) REFERENCES houses (id),
FOREIGN KEY (person_id) REFERENCES people (id)
) ENGINE=INNODB;
Then searching for people will be as easy as this:
SELECT p.*
FROM houses h
JOIN people_houses ph ON ph.house_id = h.id
JOIN people p ON p.id = ph.person_id
WHERE h.name = 'SomeArbitraryHouseImInterestedIn';
No more false positives, and they all lived happily ever after.

Answer 2

The nice solution is to redesign your schema so that you have the following tables:
People
------
PeopleID (PK)
...
PeopleHouses
------------
PeopleID (PK) (FK to People)
HouseID (PK) (FK to Houses)
Houses
------
HouseID (PK)
...

Answer 3

Short Term Solution
For your immediate problem, the FIND_IN_SET function is what you want to use for joining:
For People
SELECT p.*
FROM PEOPLE p
JOIN HOUSES h ON FIND_IN_SET(p.name, h.people)
WHERE h.name = ?
For Houses
SELECT h.*
FROM HOUSES h
JOIN PEOPLE p ON FIND_IN_SET(h.name, p.houses)
WHERE p.name = ?
Long Term Solution
Is to properly model this by adding a table to link houses to people, because you're likely storing redundant relationships in both tables:
CREATE TABLE people_houses (
house_id int,
person_id int,
PRIMARY KEY (house_id, person_id),
FOREIGN KEY (house_id) REFERENCES houses (id),
FOREIGN KEY (person_id) REFERENCES people (id)
)

Answer 4

The problem is that you have to use another schema, like the one proposed by #RedFilter. You can see it as:
People table:
PeopleID
otherFields
Houses table:
HouseID
otherFields
Ownership table:
PeopleID
HouseID
otherFields
Hope that helps,

Answer 5

Hi you just change the table name places, left side is People and then right side is Houses:
SELECT People.*
FROM People
LEFT JOIN Houses ON Houses.People Like CONCAT(CONCAT('%', People.Name), '%')
WHERE House.Name = 'SomeArbitraryHouseImInterestedIn'