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

Try This

 SET @old_balance = 0;
    UPDATE tableName SET 
    Total =  
    CASE
      WHEN Col3 = 'A' and Col4 <> 'Z' THEN Col1 + Col2
      WHEN Col3 = 'B' and Col4 <> 'Z' THEN Col1 - Col2
      WHEN Col3 = 'C' and Col4 <> 'Z' THEN Col1 * Col2
    END,
    Balance = 
    CASE
      WHEN Col3 = 'A' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 + Col2)
      WHEN Col3 = 'B' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 - Col2)
      WHEN Col3 = 'C' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 * Col2)
    END,
    @old_balance := 
    CASE
      WHEN Col3 = 'A' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 + Col2)
      WHEN Col3 = 'B' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 - Col2)
      WHEN Col3 = 'C' and Col4 <> 'Z' THEN 
      @old_balance + (Col1 * Col2)
    END
    WHERE t1.id > 1;