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仅适用于catid=$category_id。在此处忽略启动此catid IN ( SELECT id FROM #__categories WHERE parent_id=$category_id )输出所有行和特征= 1的位置。如何将featured=1条件添加到catid IN？

所以基本上它现在看起来像这样：

$query = "SELECT * FROM #__content WHERE featured=1 and catid=$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所需的评估顺序：

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，因此当(featured=1 and catid=$category_id)为真，或者catid列在IN列表中时，没有括号的表达式为真由子查询指定。

Answer 2

加入怎么样？

$query = "SELECT * FROM #__content WHERE featured=1 and catid=$category_id";
$query2 = "
SELECT * FROM #__content as con
LEFT JOIN #__categories as cat
on con.cat_id =cat.category_id
WHERE cat.parent_id=$category_id;"

在查询中将条件添加到“IN”

2 个答案: