SQL加入2个表：1`ON`对2`ON`

Question

我有一个类似的查询：

select gift.id as giftId, gift.title, count(vouchercode.id) as stock, vouchertemplate.unlimited, gift.voucherTemplate, vouchertemplate.id as voucherId,vouchertemplate.title
from gift 
inner join vouchertemplate 
left join vouchercode 
on gift.voucherTemplate = vouchertemplate.id 
on vouchertemplate.id = vouchercode.template 
and vouchercode.given = 0 
where gift.id in (13,14,15,16)

我发现这并没有给我正确的结果。看来on gift.voucherTemplate = vouchertemplate.id无效。我在左连接之前需要它。所以我不能把所有的连接条件放在一起？我指定了要加入的表名和列，所以我想知道为什么会有区别？

以下查询为我提供了正确的结果。

select gift.id as giftId, gift.title, count(vouchercode.id) as stock, vouchertemplate.unlimited, gift.voucherTemplate, vouchertemplate.id as voucherId,vouchertemplate.title
from gift 
inner join vouchertemplate 
on gift.voucherTemplate = vouchertemplate.id  <<< DIFF HERE
left join vouchercode 
on vouchertemplate.id = vouchercode.template 
and vouchercode.given = 0 
where gift.id in (13,14,15,16)