MySQL join query only one row with reference table - mysql

Question

Here is my 5 tables.
product
id(PK)
name
description
id(PK)
body
price
id(PK)
currency
product_description
id(PK)
product_id
description_id
product_price
id(PK)
product_id
price_id
Table product, description, price is where stored actual data.
And table product_description and product_price is reference table.
My expected query result like this.
product_id | product_name | description_body | price_currency
Current table's data
product
+----+----------------+
| id | name |
+----+----------------+
| 1 | first product |
| 2 | second product |
| 3 | third product |
+----+----------------+
description
+----+------------+
| id | body |
+----+------------+
| 1 | first desc |
| 2 | second des |
| 3 | third desc |
+----+------------+
price
+----+-------------+
| id | currency |
+----+-------------+
| 1 | first cur |
| 2 | second cur2 |
| 3 | third cur |
+----+-------------+
product_description
+----+------------+----------------+
| id | product_id | description_id |
+----+------------+----------------+
| 1 | 1 | 1 |
| 2 | 2 | 2 |
| 3 | 3 | 3 |
+----+------------+----------------+
product_price
+----+------------+----------+
| id | product_id | price_id |
+----+------------+----------+
| 1 | 1 | 1 |
| 2 | 2 | 2 |
| 3 | 3 | 3 |
+----+------------+----------+
Query
SELECT product.*, description.body, price.currency FROM product
LEFT JOIN product_description ON product.id = product_description.product_id
LEFT JOIN product_price ON product.id = product_price.product_id
LEFT JOIN description ON description.id = product_description.description_id
LEFT JOIN price ON price.id = product_price.price_id
Result
+----+----------------+------------+-------------+
| id | name | body | currency |
+----+----------------+------------+-------------+
| 1 | first product | first desc | first cur |
| 2 | second product | second desc| second cur2 |
| 3 | third product | third desc | third cur |
+----+----------------+------------+-------------+
In that moment, If I insert into product_description one more row that has product_id=1 and re querying, it shows many rows that product_id=2.
After insert into product_description values(4, 2, 1)
product_description
+----+------------+----------------+
| id | product_id | description_id |
+----+------------+----------------+
| 1 | 1 | 1 |
| 2 | 2 | 2 |
| 3 | 3 | 3 |
| 4 | 2 | 1 |
+----+------------+----------------+
After join query.
+----+----------------+------------+-------------+
| id | name | body | currency |
+----+----------------+------------+-------------+
| 1 | first product | first desc | first cur |
| 2 | second product | second desc | second cur2 |
| 2 | second product | first desc | second cur2 |
| 3 | third product | third desc | third cur |
+----+----------------+------------+-------------+
You know that because of product=2 row's count is 2 in product_description, result print all of it.
But I want to only last one rows that contain product=2.
Maybe limit or distinct is useful, I don't know it is possible.
Can I use limit or distinct in join query?

Answer 1

You can try using correlated subquery
SELECT product.*, description.body, price.currency FROM product
LEFT JOIN
( select * from product_description
where product_description.id in (select max(id) from product_description b
where product_description.product_id=b.product_id)
) as x ON product.id = x.product_id
LEFT JOIN product_price ON product.id = product_price.product_id
LEFT JOIN description ON description.id = x.description_id
LEFT JOIN price ON price.id = product_price.price_id