如果第二个表中至少有4条记录，则从两个表中选择记录

Question

I have 2 tables and i want to fetch data based on below condition:

• Table1 has multiple product records.
• Table2 contains various Size option for products and can not have more or less than 4 rows.

Now, i want to fetch those products which do not have entry or do not have exact 4 entries.

Table Structure is as below:

Table1

id   name  color  price   instock
----------------------------------
 1   rice   white  1200    1
 2   shoe   brown  2500    1
 3   belt   red    5200    1

Table2

  id   size   pid
 -----------------
  1     5     1
  2     10    1
  3     4     1 
  4     15    1
  5     7     2

Now Query shall fetch product with ID 2 and 3 as they have records less than 4 and no record resp.

I was using below query to fetch products which have no records in Table2

SELECT p.* FROM `Table1` p LEFT JOIN `Table2` t ON p.id = t.pid  WHERE 
t.pid IS NULL

Answer 1

SELECT p.id, p.name, p.color, p.price, p.instock, count(t.*) 
FROM `Table1` p 
LEFT JOIN `Table2` t 
ON p.id = t.pid  
GROUP BY p.id, p.name, p.color, p.price, p.instock
HAVING count(t.*) < 4