MySQL Skills

最新推荐文章于 2025-08-09 21:15:38 发布

原创最新推荐文章于 2025-08-09 21:15:38 发布 · 507 阅读

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1.MySQL 不能在一个语句里使用别名：
解决办法：使用变量来替代。
Exampls:
SELECT net,tax_rate,net / tax_rate AS tax,net + tax AS grossFROM items
But that dosent work, mysql dosent allow an alias in the SELECTstatement (says it cant find a field called tax), which is kind ofannoying as it means i have to duplicate all my calculations like this:SELECT net,tax_rate,net / tax_rate AS tax,net + (net / tax_rate) AS grossFROM items
Solved: SELECT net, tax_rate, @tax:=(net / tax_rate) AS tax, net + @tax AS gross FROM items