MySql comma seperated values and using IN to select data - mysql

Question

I store destinations a user is willing to ship a product to in a varchar field like this:
"userId" "destinations" "product"
"1" "US,SE,DE" "apples"
"2" "US,SE" "books"
"3" "US" "mushrooms"
"1" "SE,DE" "figs"
"2" "UK" "Golf Balls"
I was hoping this query would return all rows where US was present. Instead it returns only a single row.
select * from destinations where destinations IN('US');
How do I get this right? Am I using the wrong column type? or is it my query that's failing.
Current Results
US
Expected Results
US,SE,DE
US,SE
US

Answer 1

Try with FIND_IN_SET
select * from destinations where FIND_IN_SET('US',destinations);

Answer 2

Unfortunately, the way you've structured your table, you'll have to check for a pattern match for "US" in your string at the beginning, middle, or end.
One way you can do that is using LIKE, as follows:
SELECT *
FROM destinations
WHERE destinations LIKE ('%US%');
Another way is using REGEXP:
SELECT *
FROM destinations
WHERE destinations REGEXP '.*US.*';
Yet another is using FIND_IN_SET, as explained by Sadkhasan.
CAVEAT
None of these will offer great performance or data integrity, though. And they will all COMPOUND their performance problems when you add criteria to your search.
E.g. using FIND_IN_SET, proposed by Sadkhasan, you would have to do something like:
SELECT * FROM destinations
WHERE FIND_IN_SET('US',destinations)
OR FIND_IN_SET('CA',destinations)
OR FIND_IN_SET('ET',destinations);
Using REGEXP is a little better, though REGEXP is innately slow:
SELECT *
FROM destinations
WHERE destinations REGEXP '.*US|CA|ET.*';
SO WHAT NOW?
Your best bet would be switching to a 3NF design with destinations applying to products by splitting into 2 tables that you can join, e.g.:
CREATE TABLE products (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
userId INT NOT NULL REFERENCES users(id),
name VARCHAR(255) NOT NULL
) TYPE=InnoDB;
Then you would add what's called a composite key table, each row containing a productId and a single country, with one row per country.
CREATE TABLE product_destinations (
productId INT NOT NULL REFERENCES products(id),
country VARCHAR(2) NOT NULL,
PRIARY KEY (productId, country)
) TYPE=InnoDB;
Data in this table would look like:
productId | country
----------|--------
1 | US
1 | CA
1 | ET
2 | US
2 | GB
Then you could structure a query like this:
SELECT p.*
FROM products AS p
INNER JOIN product_destinations AS d
ON p.id = d.productId
WHERE d.country IN ('US', 'CA', 'ET')
GROUP BY p.id;
It's important to add the GROUP (or DISTINCT in the SELECT clause), as a single product may ship to multiple countries, resulting in multiple row matches - aggregation will reduce those to a single result per product id.
An added bonus is you don't have to UPDATE your countries column and do string operations to determine if the country already exists there. You can let the database do that for you, and INSERT - preventing locking issues that will further compound your problems.

Answer 3

You can use this if your destinations have just two caracters of the countries.
SELECT * FROM destinations WHERE destinations LIKE ('%US%')
to add other country
SELECT * FROM destinations WHERE destinations LIKE ('%US%')
AND destinations LIKE ('%SE%')
^^^--> you use AND or OR as you want the result.