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1. This error message can occur with a DROP INDEX statement. Indexes with identical names were created for separate tables. Therefore the name of the index to be deleted is not unique.
2. There is only a named single-column index for this column. The attempt was made to delete the index for this column without specifying its name.
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1. Specify the name of the table to which the index to be deleted refers in the <DROP INDEX statement>.
2. Delete the index specifying its name.