Using an overall WHERE clause when using UNIONS in sql
I am trying to return the MATCH() AGAINST() 开发者_JS百科results against several tables using UNIONS, the only problem is some rows return a relevance of 0, I want to exclude these. After the unions is there a way to use 'WHERE relevance > 0'
Below is a bit of my 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
So is there anyway I can add WHERE relevance > 0 before the ORDER BY
many thanks
Try using a derived table
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
you could add it to each query or at the end:
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)
WHERE relevance > 0
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
WHERE relevance > 0
ORDER BY relevance DESC
SELECT search, relevance 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
) D
WHERE relevance > 0
ORDER BY relevance DESC
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