如何从嵌套连接查询中进行选择

I have these two queries and I want to join them together in order to let the user filter the first query according to the second one

first query :

SELECT t1 . * 
FROM car t1
left outer JOIN rent ON t1.carId = rent.carId
WHERE NOT 
EXISTS (

SELECT NULL 
FROM rent t2
WHERE t1.carId = t2.carId

)
OR not (
rent.startdate > '$to'
OR rent.enddate < '$from'
)

second query:

SELECT carId,model,fuelconsumption,type,picture,color,price,region FROM  car WHERE model ='$m' OR type='$t' OR price='$p' OR color = '$c' ORDER BY model,type,price,color DESC

the two queries are giving correct answers separately

I am not sure to understand your request, but if you want to merge the two queries, you should do like this:

select t1.*
from car t1
left outer join rent on t1.carId = rent.carId
where 
(
  not exists
  (
    select null
    from rent t2
    where t1.carId = t2.carId
  )
  or not
  (
    rent.startdate > '$to'
    or rent.enddate < '$from'
  )
)
and 
(
  model ='$m'
  OR type='$t'
  OR price='$p'
  OR color = '$c'
)
order by model,type,price,color desc