Why not show my results when i use not squeal with and-CodePudding

Why not show my results when i use not squeal with and in this case

SELECT 
'999' as A,
'999' AS B,
'000' AS C,
'000' as D
WHERE
A <> '999'
and B <> '999'
and C <> '999'
AND D <> '999'

This terminal results enter image description here

CodePudding user response：

Basically, we can't use WHERE clause to filter the column that dynamically evaluates. Try to use HAVING instead.

SELECT 
'999' as A,
'999' AS B,
'000' AS C,
'000' as D
HAVING
A <> '999'
and B <> '999'
and C <> '999'
AND D <> '999'

CodePudding user response：

May be because you have set the values for A,B,C,D and sql processor does not see any ones. And you use 'AND' - so it means that the condition should be resolved only together, for all values. So that is why you don`t see C and D.

CodePudding user response：

You would need to implement a derived table such as:

select A, B, C, D
from (
    select 
    '999' as A,
    '999' as B,
    '000' as C,
    '000' as D
)t
where
A <> '999'
and B <> '999'
and C <> '999'
and D <> '999';