SQL 语句中使用具有子句中的条件时出错

Question

I have a products table with columns id , price , category , and city . I need to find the count of the cheapest veggies in a Barcelona city.

I tried this SQL query, but I get an error:

SELECT COUNT( * ) 
FROM products 
HAVING lower(category) = 'veggies' AND lower(city) = 'Barcelona' 
   AND price = (SELECT MIN(price)
                FROM products
                WHERE lower(category) = 'veggies' and lower(city) = 'Barcelona');

Can you please let me know where I am going wrong?

Answer 1

Look at the documentation of sql

You need a where not a having here, and it comes before the joins

SELECT COUNT( * ) 
FROM products pd 
Where lower(category) = 'veggies' AND lower(city) = 'Barcelona' 
AND price = (
   SELECT MIN(price) 
   FROM products pd
   WHERE lower(category) = 'veggies' and lower(city) = 'Barcelona'
);

Answer 2

The HAVING keyword is used when you're doing a group by, and need a where clause.

SELECT COUNT( * ) 
FROM products 
WHERE city = 'Barcelona' and categories = 'veggies'
ORDER BY price asc

This will give you the cheapest veggies in Barcelona.