// this column will not be able to run ALTER
		// see https://stackoverflow.com/questions/19460912/the-object-df-is-dependent-on-column-changing-int-to-double/19461205#19461205
		// may we need to create another PR to fix it, see https://github.com/go-gorm/sqlserver/pull/106
		tests = []TestCase{
			{name: "unique to notUnique", from: &UniqueStruct3{}, to: &UniqueStruct1{}, checkFunc: checkNotUnique},

	relation.Type = Many2Many

	var (
		err             error
		joinTableFields []reflect.StructField
		fieldsMap       = map[string]*Field{}
		ownFieldsMap    = map[string]*Field{} // fix self join many2many
		referFieldsMap  = map[string]*Field{}
		joinForeignKeys = toColumns(field.TagSettings["JOINFOREIGNKEY"])
		joinReferences  = toColumns(field.TagSettings["JOINREFERENCES"])
	)