Select AS not working in interbase

Question

works

select payeeid, EXTRACT(WEEKDAY FROM checkdate) as DOW, 
(bankcleared - checkdate) as DateDiff  
from Master  
where (bankcleared is not null)  
order by payeeid, DOW, DateDiff  

adding DateDiff to Where - does not work

select payeeid, EXTRACT(WEEKDAY FROM checkdate) as DOW, 
(bankcleared - checkdate) as DateDiff  
from Master  
where (bankcleared is not null)  AND (DateDiff >= 1)  
order by payeeid, DOW, DateDiff  

Answer 1

You can only use column aliases in GROUP BY, ORDER BY, or HAVING clauses.

Standard SQL doesn't allow you to refer to a column alias in a WHERE clause. This restriction is imposed because when the WHERE code is executed, the column value may not yet be determined.

Try this

select payeeid, EXTRACT(WEEKDAY FROM checkdate) as DOW, 
(bankcleared - checkdate) as DateDiff
from Master
where (bankcleared is not null) AND ((bankcleared - checkdate)>= 1)
order by payeeid, DOW, DateDiff 

For more info go through these links

Can you use an alias in the WHERE clause in mysql?

Unknown Column In Where Clause

Answer 2

select payeeid, 
       EXTRACT(WEEKDAY FROM checkdate) as DOW, 
       (bankcleared - checkdate) as DateDiff
from Master
WHERE (bankcleared is not null) 
AND   ((bankcleared - checkdate)>= 1)
Order by  payeeid, DOW, DateDiff