How can I drop the "Unique Key Constraint" on a column of a MySQL table using phpMyAdmin?
A unique constraint is also an index.
SHOW INDEX FROM tbl_name to find out the name of the index. The name of the index is stored in the column called
key_name in the results of that query.
Then you can use DROP INDEX:
DROP INDEX index_name ON tbl_name
or the ALTER TABLE syntax:
ALTER TABLE tbl_name DROP INDEX index_name