需要Laravel查询说明

Question

任何人都可以解释一下IF(transactions.retail_cost > 0,1,0)从以下查询中的含义吗？

$query = Distributors::selectRaw(
    "distributors.name,distributors.group_id,"
    . "distributors.pay,"
    . "SUM(IF(transactions.retail_cost > 0,1,0)) AS trans_number"
);