MySql查询运行余额校正

I don't think this can be done using set based code since you need read ahead and read back. Something procedural could work. Using a cursor and a temporary table I can pretty much accomplish that (you need to add stuff to ensure that cumulative balance does not go negative). From what you say the first transaction can never take the balance negative but I would check for that. Note well the takes from the credit pool may come from a later date than the debit the take is compensating for - since the balance can never go negative then that should not be a problem (sic). And of course I would not expect the performance to be great.

DROP TABLE IF EXISTS T;
create table t
(trx_no int, trx_date date,    Opening int,debit int,  credit int);
insert into t values
(1    ,   '2019-10-01' , 200  ,   0     ,  100),    
(2    ,   '2019-10-02' , 200  ,   0     ,  100),    
(3    ,   '2019-10-03' , 200  ,   100   ,  0  ),     
(4    ,   '2019-10-03' , 200  ,   400   ,  0  ),    
(5    ,   '2019-10-03' , 200  ,   0     ,  200),      
(6    ,   '2019-10-04' , 200  ,   0     ,  100),      
(7    ,   '2019-10-05' , 200  ,   100   ,  0  ),
(8    ,   '2019-10-05' , 200  ,   0     ,  400);

DROP TABLE IF EXISTS stmT;
create table stmt
(trx_no int, trx_date date,    Opening int,debit int,  credit int, cumbal int);




drop procedure if exists p;
delimiter $$
create procedure p()
begin

 declare v_trx_no int;
 declare v_dt date;
 declare v_debit int;
 declare v_credit int;

 declare h_trx_no int;
 declare h_dt date;
 declare h_credit int;

 declare opbal int;
 declare rbal  int;
 declare done int default 0;
 declare cur cursor for select trx_no,trx_date,debit,credit from t order by trx_date,trx_no;
 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

 select opening into opbal from t order by trx_no limit 1;
 set rbal = opbal;
 drop table if exists creditpool;
 create temporary table if not exists creditpool as select trx_no,trx_date,credit,0 as used from t where  credit > 0; 
 #select * from creditpool;
    open cur;
    cursorloop:loop
        fetch cur into v_trx_no,v_dt,v_debit,v_credit;
         if done = true then  
        leave cursorloop;
         end if;  
         if v_credit > 0 and exists (select 1 from creditpool where trx_no = v_trx_no and used = 0) then 
             if v_credit > 0 then
                 insert into stmt values (v_trx_no,v_dt,opbal,v_debit,v_credit, rbal + v_credit);
                 set rbal = rbal + v_credit;
                 update creditpool set used = 1 where trx_no = v_trx_no; 
            end if;
         end if;
         if v_debit > 0 and v_debit <= rbal then
             insert into stmt values (v_trx_no,v_dt,opbal,v_debit,v_credit, rbal - v_debit);
             set rbal = rbal - v_debit;
         elseif v_debit > 0 and v_debit > rbal then
             poolloop: loop
                        select trx_no,trx_date,credit
                            into h_trx_no,h_dt,h_credit
                            from creditpool
                            where used = 0 
                            order by trx_date,trx_no limit 1;
                        insert into stmt values (h_trx_no,h_dt,opbal,0,h_credit, rbal + h_credit);
                        set rbal = rbal + h_credit;
                        update creditpool set used = 1 where trx_no = h_trx_no; 

                        if v_debit <= rbal then
                            insert into stmt values (v_trx_no,v_dt,opbal,v_debit,v_credit, rbal - v_debit);
                            set rbal = rbal - v_debit;
                            leave poolloop;
                        end if;
             end loop poolloop;           
         end if;
    end loop cursorloop;
    close cur;
end $$
delimiter ;
truncate stmt;
call p();
select * from stmt;

+--------+------------+---------+-------+--------+--------+
| trx_no | trx_date   | Opening | debit | credit | cumbal |
+--------+------------+---------+-------+--------+--------+
|      1 | 2019-10-01 |     200 |     0 |    100 |    300 |
|      2 | 2019-10-02 |     200 |     0 |    100 |    400 |
|      3 | 2019-10-03 |     200 |   100 |      0 |    300 |
|      5 | 2019-10-03 |     200 |     0 |    200 |    500 |
|      4 | 2019-10-03 |     200 |   400 |      0 |    100 |
|      6 | 2019-10-04 |     200 |     0 |    100 |    200 |
|      7 | 2019-10-05 |     200 |   100 |      0 |    100 |
|      8 | 2019-10-05 |     200 |     0 |    400 |    500 |
+--------+------------+---------+-------+--------+--------+
8 rows in set (0.00 sec)

请注意，结果与您想要的结果略有不同，因为仅在需要时才会进行拍摄.