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create table mytable (
ColumnA varchar(20),
ColumnB varchar(20)
);
insert into mytable values
('ABC', '1'),
('oo', 'bb'),
('oo', NULL),
(NULL, 'bb'),
(NULL, NULL),
('BCD', '2'),
('bb', 'oo');
7 rows affected
SELECT *
FROM mytable
WHERE (
columnA <> columnB
AND NOT (columnA = 'bb' and columnB = 'oo'
or columnA = 'oo' and columnB = 'bb')
) OR columnA IS NULL OR columnB IS NULL
| ColumnA | ColumnB |
|---|---|
| ABC | 1 |
| oo | null |
| null | bb |
| null | null |
| BCD | 2 |