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

SET @prev_id = 1;
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 
  (SELECT Balance FROM tableName WHERE id = @prev_id) + (Col1 + Col2)
  WHEN Col3 = B and Col4 <> Z THEN 
  (SELECT Balance FROM tableName WHERE id = @prev_id) + (Col1 - Col2)
  WHEN Col3 = C and Col4 <> Z THEN 
  (SELECT Balance FROM tableName WHERE id = @prev_id) + (Col1 * Col2)
END,
@prev_id := id

WHERE t1.id > 1;