sql - 在 sql 中使用 UNIONS 时使用整体 WHERE 子句

Question

我正在尝试使用 UNIONS 针对多个表返回 MATCH() AGAINST() 结果，唯一的问题是某些行返回 0 的相关性，我想排除这些。在工会之后有一种方法可以使用 'WHERE relevance > 0'

下面是我的一些SQL

SELECT pages.content AS search, page_info.url AS link, MATCH(pages.content) AGAINST('Wales') as relevance 
FROM page_content
LEFT JOIN pages ON (page_info.page = pages.id)

UNION

SELECT products_real.name AS search, products_real.event AS link, MATCH(products_real.name, products_real.description) AGAINST ('Wales') as relevance
FROM product_real

ORDER BY relevance DESC

那么无论如何我可以在 ORDER BY 之前添加 WHERE relevance > 0

非常感谢

Answer 1

尝试使用派生表

SELECT * 
FROM
  (SELECT 
    pages.content AS search, 
    page_info.url AS link, 
    MATCH(pages.content) AGAINST('Wales') as relevance  
  FROM page_content 
  LEFT JOIN pages ON (page_info.page = pages.id) 
  UNION 
  SELECT 
    products_real.name AS search, 
    products_real.event AS link, 
    MATCH(products_real.name, products_real.description) AGAINST ('Wales') as relevance 
  FROM product_real) myQuery
Where myQuery.relevance <> 0
ORDER BY myQuery.relevance DESC