} else {
		name := v.Name()
		c := stmt.Clauses[name]
		c.Name = name
		v.MergeClause(&c)
		stmt.Clauses[name] = c
	}
}

// AddClauseIfNotExists add clause if not exists
func (stmt *Statement) AddClauseIfNotExists(v clause.Interface) {
	if c, ok := stmt.Clauses[v.Name()]; !ok || c.Expression == nil {
		stmt.AddClause(v)
	}
}

// BuildCondition build condition

				column = f.DBName
			}
		}
	}

	if len(tx.Statement.Selects) != 1 {
		fields := strings.FieldsFunc(column, utils.IsValidDBNameChar)
		tx.Statement.AddClauseIfNotExists(clause.Select{
			Distinct: tx.Statement.Distinct,
			Columns:  []clause.Column{{Name: column, Raw: len(fields) != 1}},
		})
	}
	tx.Statement.Dest = dest
	return tx.callbacks.Query().Execute(tx)
}