Mysql variable in where clause - mysql

Question

When i add last row "and #summ > 0 (any condition)"
It returns empty result.
What i do wrong ? How right pass #summ into where clause ?
select
nore.nis as nore_curent,
field_funds.value,
(select #summ :=
sum(field_amount.value - field_amount_tip.value)
from
nore
inner join field_project on nore.nis = field_project.id
inner join field_funds on field_funds.id = field_project.target_id
inner join field_amount on nore.nid = field_data_field_amount.id
inner join field_amount_tip on nore.nis = field_amount_tip.id
where
nore.`s` = 1
and
nore.`t` = 'p'
and
field_project.target_id = nore_curent) as amount
from
nore
inner join field_funds on nore.nis = field_funds.id
where
nore.`s` = 1
and
nore.`t` = 'pp'
and #summ > 0

Answer 1

It's worthwhile to remaind some basics related to a conceptual (or a logical) order of evaluation of a Select statement- here:http://tinman.cs.gsu.edu/~raj/sql/node22.html
The order is:
FROM
WHERE
GROUP BY
HAVING
ORDER BY
SELECT
The WHERE clause is evaluated (executed) before the SELECT clause.
A value of #summ is calculated in SELECT clause (of the main query), so it's value is unknown when DMBS evaluates the WHERE clause.
Unknown = NULL
Therefore this query won't work as expected.
Rewrite the query into:
select
nore.nis as nore_curent,
field_funds.value,
(select sum(field_amount.value - field_amount_tip.value)
from
nore
inner join field_project on nore.nis = field_project.id
inner join field_funds on field_funds.id = field_project.target_id
inner join field_amount on nore.nid = field_data_field_amount.id
inner join field_amount_tip on nore.nis = field_amount_tip.id
where
nore.`s` = 1
and
nore.`t` = 'p'
and
field_project.target_id = nore_curent) as amount
from
nore
inner join field_funds on nore.nis = field_funds.id
where
nore.`s` = 1
and
nore.`t` = 'pp'
and 0 < (select sum(field_amount.value - field_amount_tip.value)
from nore
inner join field_project on nore.nis = field_project.id
inner join field_funds on field_funds.id = field_project.target_id
inner join field_amount on nore.nid = field_data_field_amount.id
inner join field_amount_tip on nore.nis = field_amount_tip.id
where
nore.`s` = 1
and
nore.`t` = 'p'
and
field_project.target_id = nore_curent
)