mysql - 如何将多个查询减少为一个查询

Question

Query 1: select item_no from hdd where item_no='$in' and id != '$id'

Query 2: select sr from hdd where sr='$hd'

Query 3: select item_no from hdd where casing_no='$c' and id != '$id'

要求的结果:

Q1 = num_rows = 0
Q2 = num_rows <> 0
Q3 = num_rows = 0

如何在单个查询中执行上述任务？ ？

这样做:

SELECT id FROM hdd WHERE status='1' AND item_no='$in' AND FIND_IN_SET('$hd', sr)<>0 AND casing='$c' AND id<>'111'

Answer 1

也许试试

SELECT id FROM hdd
WHERE ( (id <> '$id' AND (item_no = '$in' OR casing_no = '$c') ) OR sr='$hd');

where 列的分割是

在哪里
任何一个
--id 不等于 '$id' 并且它匹配 item_no = '$in' 或者它匹配 casing_no = '$c'
或者
--匹配第二个查询，sr='$hd'