code: func (engine *Engine) CondDeleted(colName string) builder.Cond {
  	if engine.dialect.DBType() == core.MSSQL {
  		return builder.IsNull{colName}
  	}
  	return builder.IsNull{colName}.Or(builder.Eq{colName: zeroTime1})
  }
docs: // CondDeleted returns the conditions whether a record is soft deleted.