Question

I am trying to update 3 different columns in a table based on 3 different conditions in the where clause. (I have the updated data in a different table, so I am joining them on the primary keys)

For example, if I did not have a value previously in field1 for a customer but now I do,
I should be able to update the column ‘field1’. Similarly, I would like to update columns field2 and field3.

Can I accomplish this in a single Update statement.

To Update one column you can write something like this:

Update tblCustomer 
SET tblCustomer.Order_Date = tblCustomerInfo.Order_Date
FROM tblCustomer 
LEFT JOIN tblCustomerInfo ON (tblCustomer.CustomerID = tblCustomerInfo.CustomerID)
WHERE tblCustomer.Order_Date <> tblCustomerInfo.Order_Date 
  AND tblCustomer.Order_Date is NULL;

How about updating 3 different Columns in single go based on different where conditions
(if the data was missing for that column was missing previously, and is now available)

Answer 1

UPDATE categories
    SET display_order = CASE id
        WHEN 1 THEN 3
        WHEN 2 THEN 4
        WHEN 3 THEN 5
    END,
    title = CASE id
        WHEN 1 THEN 'New Title 1'
        WHEN 2 THEN 'New Title 2'
        WHEN 3 THEN 'New Title 3'
    END
WHERE id IN (1,2,3)