Update the total based on the previous row of balance

Question

This is the database data.

Name   id  Col1  Col2  Col3 Col4 Total  Balance
Row1   1    6     1     A     Z     -      - 
Row2   2    2     3     B     Z     -            


        

Answer 1

UPDATE tableName t1 SET 
Total =  
CASE
  WHEN t1.Col3 = "A" and t1.Col4 <> "Z" THEN t1.Col1 + t1.Col2
  WHEN t1.Col3 = "B" and t1.Col4 <> "Z" THEN t1.Col1 - t1.Col2
  WHEN t1.Col3 = "C" and t1.Col4 <> "Z" THEN t1.Col1 * t1.Col2
END
Balance = 
CASE
  WHEN t1.Col3 = "A" and t1.Col4 <> "Z" THEN 
  (SELECT t2.Balance FROM tableName t2 
    WHERE t2.id = (select max(t3.id) from tableName t3 where t3.id < t1.id))
    + (t1.Col1 + t1.Col2)
  WHEN t1.Col3 = "B" and t1.Col4 <> "Z" THEN 
  (SELECT t2.Balance FROM tableName t2 
    WHERE t2.id = (select max(t3.id) from tableName t3 where t3.id < t1.id))
    + (t1.Col1 - t1.Col2)
  WHEN t1.Col3 = "C" and t1.Col4 <> "Z" THEN 
  (SELECT t2.Balance FROM tableName t2 
    WHERE t2.id = (select max(t3.id) from tableName t3 where t3.id < t1.id))
    + (t1.Col1 * t1.Col2)
END
WHERE t1.id > 1;