Найдите дубликаты колонки MySQL
SELECT name, COUNT(*) c FROM table GROUP BY name HAVING c > 1;
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SELECT name, COUNT(*) c FROM table GROUP BY name HAVING c > 1;SELECT
col1, COUNT(col1),
col2, COUNT(col2)
FROM
table_name
GROUP BY
col1,
col2
HAVING
(COUNT(col1) > 1) AND
(COUNT(col2) > 1);