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 varchar_col
FROM table
GROUP BY varchar_col
HAVING COUNT(*) > 1;
SELECT col, COUNT(col) FROM table_name GROUP BY col HAVING COUNT(col) > 1;SELECT
col,
COUNT(col)
FROM
table_name
GROUP BY col
HAVING COUNT(col) > 1;SELECT
col1, COUNT(col1),
col2, COUNT(col2)
FROM
table_name
GROUP BY
col1,
col2
HAVING
(COUNT(col1) > 1) AND
(COUNT(col2) > 1);
## Find ALL duplicate recods by value (without grouping them by value) ##
# to find the duplicate,
# replace all instances of tableName with your table name
# and all instances of duplicateField with the field name where you look for duplicates
SELECT t1.*
FROM tableName AS t1
INNER JOIN(
SELECT duplicateField
FROM tableName
GROUP BY duplicateField
HAVING COUNT(duplicateField) > 1
)temp ON t1.duplicateField = temp.duplicateField
order by duplicateField