Mysql ERROR 1241（21000）：操作数应包含1列

Question

I have Customer Groups with Number-Ranges (from Customernumber, to Customernumber).

select g.id,
(select count(*), sum(sales)
FROM transactions t1 
where t1.customernumber between g.from_customernumber and g.to_customernumber)
from customer_groups g

When selecting this i get this error

ERROR 1241 (21000): Operand should contain 1 column(s)

What can i do to fix this? I've read some threads about this but I didn't find a solution for this.

Best regards!

Answer 1

MySQL is expecting a single column from your subquery, ie the SELECT in the brackets can only SELECT for a single column.

In your example, you could use two subqueries, one that returns the count and one other that returns the sum, but you could also rewrite your query as this:

SELECT g.id, COUNT(t1.customernumber), SUM(sales)
FROM
  customer_groups g LEFT JOIN transactions t1
  ON t1.customernumber between g.from_customernumber and g.to_customernumber