-- setup
CREATE TABLE tabulka (`id` int, `balik` varchar(100));
INSERT INTO tabulka (`id`, `balik`) VALUES (154602, 'CV029222553CZ');
 
-- before
SELECT 'before';
SELECT * FROM tabulka;
 
-- update
UPDATE tabulka SET balik = 'abc' WHERE id = '154602' AND (balik != 'CV029222553CZ' OR balik is NULL) LIMIT 1;
 
-- after
SELECT ''; SELECT 'after';
SELECT * FROM tabulka;
 
-- update with equality
UPDATE tabulka SET balik = 'abc' WHERE id = '154602' AND (balik == 'CV029222553CZ' OR balik is NULL) LIMIT 1;
 
-- after
SELECT ''; SELECT 'after equality change';
SELECT * FROM tabulka;

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