Hi Sekhar,

In the code, you are creating a list of new 'Sales_Order_Line__c' object records, but you are using Database.Update() method. This is going to error out because update operation requires an existing record.

So you should be using Database.Insert instead. Here is the modified code.

trigger newSOL on Sales_Order_Line__c (Before Update) {
    
    String orderItemId,childOrderItemId;
    Decimal Diff, childAdjustedPrice,parentAdjustedPrice,parentUnitPrice,childUnitPrice,ratio,newChildAdjustedPrice;
    
    if( Trigger.isUpdate )
    {
        for (Sales_Order_Line__c orderLine: Trigger.new) {
            
            orderItemId = String.ValueOf(orderLine.OrderItemID__c);
            parentAdjustedPrice = orderLine.Adjusted_Price__c;
            parentUnitPrice = orderLine.Unit_Price__c;
            
            list<Sales_order_Line__c> childOrderLines= [select Product__c,Unit_Price__c,Adjusted_Price__c,Parent_OrderItemID__c,OrderItemID__c from Sales_Order_Line__c where Parent_OrderItemID__c =: orderItemId];
            List<Sales_Order_Line__c> recordsToBeUpdated = new List<Sales_Order_Line__c>();
            
            for(Sales_Order_Line__c l: childOrderLines)
            {
                
                childOrderItemId = String.ValueOf(l.OrderItemID__c);
                childUnitPrice = l.Unit_Price__c;
                ratio = childUnitPrice / parentUnitPrice;
                childAdjustedPrice = l.Adjusted_Price__c;
                // Diff = parentUnitPrice - parentAdjustedPrice ; 
                newChildAdjustedPrice = ratio * parentAdjustedPrice;
                
                //--- This IF Statement is redundant because childOrderItemId was initialized from String.valueOf(l.OrderItemID__c) itself therefore they will always be equal
                if(String.valueOf(l.OrderItemID__c) == childOrderItemId){
                    recordsToBeUpdated.Add(new Sales_Order_Line__c(Adjusted_Price__c= newChildAdjustedPrice));
                }
                
                Database.insert(recordsToBeUpdated);
            }
            
            
        }
    }
}