SQL query for the same value of a field

sql query for the same value of a certain field:

SELECT * FROM table WHERE col in (SELECT col FROM table GROUP BY col HAVING COUNT (col) >1);

By the way, where and having:

select * from table
where ···(Only attributes before grouping can be filtered)
group by ···(Group by a certain field)
having ···(Only Filter the overall attributes of each group after grouping and use aggregate functions)
--If you don’t use group by, the entire table will be a group by default

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