-1452: Duplicate secondary key

Explanation:

Several table rows already exist with the same values in the specified columns when a UNIQUE definition is specified, when the column attribute UNIQUE is used or when a UNIQUE definition is specified in the CREATE INDEX statement.

User Action:

Do not use the UNIQUE definition; otherwise ensure that only one table row contains a certain combination of values in the specified columns. The error message specifies the column or multiple-column index already containing the specified values.