mysql - 在查询中添加条件到 `IN`

Question

查询:

SELECT * FROM #__content WHERE featured=1 and catid=$category_id or catid IN 
( SELECT id FROM #__categories WHERE parent_id=$category_id )

Featured=1 仅在 catid=$category_id 处有效。开始这个 catid IN 的地方 ( SELECT id FROM #__categories WHERE parent_id=$category_id ) 输出所有行并且 featured=1 在这个地方被忽略。如何在 catid IN 中添加 featured=1 条件？

现在基本上它看起来像这样:

$query = "SELECT * FROM #__content WHERE featured=1 and catid=$category_id";
$query2 = "SELECT * FROM #__content WHERE catid IN 
    ( SELECT id FROM #__categories WHERE parent_id=$category_id )";

Answer 1

您需要添加括号以强制执行您需要的评估顺序:

SELECT * FROM #__content WHERE catid=$category_id OR (featured=1 AND catid IN 
( SELECT id FROM #__categories WHERE parent_id=$category_id ))

由于 AND 的优先级高于 OR，当 (featured=1 and catid=$category_id) 时，不带括号的表达式为真为真，或者 catid 在子查询指定的 IN 列表中。