Question

I quite often have rows of code like the following:

    UPDATE my_table SET name = 'x'  WHERE Original =  'a'
    UPDATE my_table SET name = 'y' WHERE Original =  'b' 
    UPDATE my_table SET name = 'z' WHERE Original = 'c'  
    UPDATE my_table SET name = 'k' WHERE Original = 'd' 
    UPDATE my_table SET name = 'm' WHERE Original = 'e'  
    UPDATE my_table SET name = 'n' WHERE Original = 'f' 

Can I combine/shorten this code into one UpDate statement – or are they best just left as they are?

Answer 1

UPDATE my_table 
SET name = 
    CASE 
        WHEN Original = 'a' THEN 'x' 
        WHEN Original = 'b' THEN 'y' 
        ... 
    END

That will update EVERY row. So if there’s an Original value you haven’t specified, it will be set to NULL. So you might want to limit the update to just those you want to update, with a WHERE clause, like so:

WHERE Original IN ('a', 'b', ...)

OR, as an alternative, you could use an ELSE statement, which leaves the name value as is, if it doesn’t have a match in the WHEN statements, like so:

    CASE 
        WHEN Original = 'a' THEN 'x' 
        WHEN Original = 'b' THEN 'y' 
        ... 
        ELSE name
    END