如何在mysql中加入两个表但不重复行

Question

I am facing one issue for getting data. I am new in Mysql. Firstly i will show my table structure

order_products
id  user_id product_id  product_name
1    1        10           Jacket1
2    1        10           Jacket2

order_products_sizes
id    order_product_id  size    qty
1          1             S      56
2          1             M      36
3          1             XL     36
4          1             2XL    56
5          2             S      32
6          2             M      28
7          2             XL     28
8          2             2XL    32
9          2             3XL    69

 My expected Output:-
product_name     S    M   XL  2XL  3XL
  JACKET1       56   36  36   56 
  JACKET2       32   28  28   32    69 

 for first row 3xl would be empty beacuse there is no size available in order_product_sizes

Actually i am using join but when i use join the rows are repeating because of joining two table that is actual behavior of joins. I have tries so far:-

SELECT order_products.product_name,
CASE 
WHEN order_product_sizes.order_product_id = order_products.id AND 
order_product_sizes.size = 'L' THEN  order_product_sizes.qty    
END AS L
from order_products
join 
order_product_sizes
on order_products_sizes.order_product_id = order_products.id;

Answer 1

You can try below - using conditional aggregation

SELECT order_products.product_name,
max(CASE 
WHEN 
order_product_sizes.size = 'S' THEN  order_product_sizes.qty    
END) AS S,
max(CASE 
WHEN 
order_product_sizes.size = 'M' THEN  order_product_sizes.qty    
END) AS M,
max(CASE 
WHEN 
order_product_sizes.size = 'XL' THEN  order_product_sizes.qty    
END) AS XL,
max(CASE 
WHEN 
order_product_sizes.size = '2XL' THEN  order_product_sizes.qty    
END) AS '2XL',
max(CASE 
WHEN 
order_product_sizes.size = '3XL' THEN  order_product_sizes.qty    
END) AS '3XL'
from order_products join order_products_sizes
on order_products_sizes.order_product_id = order_products.id
group by order_products_sizes.order_product_id