有人可以在下面的SQL中解释内部联接语法:
CREATE TABLE dataset AS
SELECT property.id
, amount.band
, amount."value"
FROM property
INNER JOIN (locality INNER JOIN amount ON locality.code = amount.code) ON (property.band = amount.band) AND (property.id = locality."UniqueId")
为什么locality
在第二个内部联接之前定义表?我从来没有遇到过这种奇怪的语法。
有没有更清晰的方法来处理相同的查询,以便有人可以轻松了解发生了什么情况?
FROM property
INNER JOIN (locality INNER JOIN amount ON locality.code = amount.code)
ON (property.band = amount.band) AND (property.id = amount."UniqueId")
是相同的
FROM property
INNER JOIN amount ON property.band = amount.band AND property.id = amount."UniqueId"
INNER JOIN locality ON locality.code = amount.code
INNER JOIN
仅当s时,您可以根据需要对其重新排序。
(有任何特定的原因需要JOIN本地化?您不选择其任何列。是某种还是EXISTS
,如果该表中有多个匹配的行,您是否要返回多行?)
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句