UPDATE TMP_COLUMNS 
    SET COLUMNNAME = (SELECT COLUMN_NAME FROM 
                      user_tab_columns usertable
                      WHERE
                      table_name = table_Name
                      AND usertable.column_id = TMP_COLUMNS.idcolumn)
    WHERE EXISTS (SELECT COLUMN_NAME 
                  FROM 
                  user_tab_columns usertable
                  WHERE
                  table_name = table_Name
                  AND usertable.column_id = TMP_COLUMNS.idcolumn);
    COMMIT;
我收到错误ORA-01427: single-row subquery returns more than one row