Question

SELECT 
   daf.id as affiliate_id,
   daf.name as affiliate_name,
   dal.name as allocation_name,
   dal.id as allocation_id,
   dal.allocation,dal.price
FROM 
     degreeamerica.affiliates daf,degreeamerica.allocations dal 
JOIN 
     (select pap.lead_price,pap.live, pap.allocation_id,pap.affiliate_id from paul.affiliates_price pap) pafp  
ON (dal.id=pafp.allocation_id and daf.id=pafp.affiliate_id) 
ORDER BY daf.id;

问题：它在on子句中说未知列daf.id，虽然我在字段列表中有这个列请帮助!!!。

Answer 1

在逗号分隔的表之前评估

JOIN个链。一直切换到显式的JOIN，它会起作用。

SELECT 
   daf.id as affiliate_id,
   daf.name as affiliate_name,
   dal.name as allocation_name,
   dal.id as allocation_id,
   dal.allocation,dal.price
FROM 
     (select pap.lead_price,pap.live, pap.allocation_id,pap.affiliate_id
      from paul.affiliates_price pap) pafp  
JOIN
     degreeamerica.affiliates daf
     ON (daf.id = pafp.affiliate_id) 
JOIN
     degreeamerica.allocations dal ON 
     ON (dal.id = pafp.allocation_id) 
ORDER BY daf.id;

Answer 2

尝试编写FROM这样的句子：

FROM paul.affiliates_price pafp JOIN
     degreeamerica.affiliates daf
     ON daf.id = pafp.affiliate_id JOIN
     degreeamerica.allocations dal 
     ON dal.id = pafp.allocation_id

子查询也是不必要的，它阻碍了索引的使用（在MySQL中）。

Answer 3

您可以将affiliates_price表'子查询用作FROM和WHERE clasue之间的表。它会以这种方式工作。

SELECT 
  daf.id as affiliate_id,
  daf.name as affiliate_name,
  dal.name as allocation_name,
  dal.id as allocation_id,
  dal.allocation,dal.price
FROM 
    degreeamerica.affiliates daf,
    degreeamerica.allocations dal,
    (select pap.lead_price,pap.live, pap.allocation_id,pap.affiliate_id from paul.affiliates_price pap) pafp     
WHERE
    dal.id=pafp.allocation_id and daf.id=pafp.affiliate_id
ORDER BY daf.id;

未知栏目问题

3 个答案: