MySQL 8.0

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CREATE TABLE test ( i_column INT, 
                    t_column DATETIME,
                    s_column TEXT );
ALTER TABLE test
ADD COLUMN check_uniqueness BINARY(128)
           GENERATED ALWAYS AS (SHA2(
                                     CONCAT(
                                            i_column IS NULL,
                                            COALESCE(i_column, 0),
                                            t_column IS NULL,
                                            COALESCE(t_column, '2000-01-01'),
                                            s_column IS NULL,
                                            COALESCE(s_column, '')
                                           ), 
                                     512
                                    )
                               ) VIRTUAL,
ADD UNIQUE INDEX checking_uniqueness (check_uniqueness);
INSERT INTO test (i_column, t_column, s_column) VALUES (NULL, NULL, NULL);
INSERT INTO test (i_column, t_column, s_column) VALUES (1, NULL, NULL);
INSERT INTO test (i_column, t_column, s_column) VALUES (NULL, '2000-01-01', NULL);
INSERT INTO test (i_column, t_column, s_column) VALUES (1, '2000-01-01', NULL);
INSERT INTO test (i_column, t_column, s_column) VALUES (NULL, NULL, 'abc');
INSERT INTO test (i_column, t_column, s_column) VALUES (1, NULL, 'abc');
INSERT INTO test (i_column, t_column, s_column) VALUES (NULL, '2000-01-01', 'abc');
INSERT INTO test (i_column, t_column, s_column) VALUES (1, '2000-01-01', 'abc');
SELECT i_column, t_column, s_column FROM test;


i_column
t_column
s_column


null
null
null

1
null
null

null
2000-01-01 00:00:00
null

1
2000-01-01 00:00:00
null

null
null
abc

1
null
abc

null
2000-01-01 00:00:00
abc

1
2000-01-01 00:00:00
abc


INSERT INTO test (i_column, t_column, s_column) VALUES (NULL, NULL, NULL);
Duplicate entry '6e500eecde81c902c4ed662d9be382cf4327e44a1062dea11da14d9b48919e02' for key 'test.checking_uniqueness'

INSERT INTO test (i_column, t_column, s_column) VALUES (1, '2000-01-01', NULL);
Duplicate entry 'dafd78672d17cbd5f630dbb9119d84bcd5eb639a895c0df1c783a41ddd40dbb6' for key 'test.checking_uniqueness'

i_column	t_column	s_column
null	null	null
1	null	null
null	2000-01-01 00:00:00	null
1	2000-01-01 00:00:00	null
null	null	abc
1	null	abc
null	2000-01-01 00:00:00	abc
1	2000-01-01 00:00:00	abc