Question

I need to query a table with a filtering condition on three columns:

select * 
from table a 
where a.order = car 
and a.color !=red 
or a.automatic !=auto

This just checks the first conditions and ignores the second one.

I just can’t get my head around it 🙁

Answer 1

Its not clear from your question but all you probably need is to wrap parens around your OR condition

Given this following table and rows

CREATE TABLE table_a 
    (
     id int primary key, 
     a_order varchar2(20), 
     color varchar2(40),
     automatic varchar2(10)
    )

/


INSERT INTO table_a VALUES (1,'car','red','auto')     /
INSERT INTO table_a VALUES (2,'car','red','manual')   /
INSERT INTO table_a VALUES (3,'car','blue','auto')    /
INSERT INTO table_a VALUES (4,'car','blue','manual') /
INSERT INTO table_a VALUES (5,'truck','red','auto')   /
INSERT INTO table_a VALUES (6,'truck','red','manual') /
INSERT INTO table_a VALUES (7,'truck','blue','auto') /
INSERT INTO table_a VALUES (8,'truck','blue','manual') /

This select statement will return records 2, 3 and 4 since they are all cars and are either blue or manual

SELECT * 
FROM   table_a a 
WHERE  a.a_order = 'car' 
       AND ( a.color != 'red' 
              OR a.automatic != 'auto' ) 

Demo

Another option is to do the following using De Morgan’s law “The negation of a disjunction is the conjunction of the negations.”

SELECT * 
FROM   table_a a 
WHERE  a.a_order = 'car' 
    AND NOT ( a.color = 'red' 
             AND a.automatic = 'auto' ) 

Demo