Question

The INSERT syntax I’ve been using is this

INSERT INTO TableName VALUES (...)

The UPDATE syntax I’ve been using is

UPDATE TableName SET ColumnName=Value WHERE ...

So in all my code, I have to generate 2 strings, which would result in something like this

insertStr = "(27, 'John Brown', 102)";
updateStr = "ID=27, Name='John Brown', ItemID=102";

and then use them separately

"UPDATE TableName SET " + updateStr + " WHERE ID=27 " +
"IF @@ROWCOUNT=0 "+
"INSERT INTO TableName VALUES (" + insertStr + ")"

It starts bothering me when I am working with tables with like 30 columns.

Can’t we generate just one string to use on both INSERT and UPDATE?

eg. using insertStr above on UPDATE statement or updateStr on INSERT statement, or a whole new way?

Answer 1

Some DBMS’ have an extension to do this but why don’t you just provide a function to do it for you? We’ve actually done this before.

I’m not sure what language you’re using but it’s probably got associative arrays where you can wrote something like:

pk{"ID"}   = "27"
val{"Name"} = "'John Brown'"
val{"ItemID"} = "102"
upsert ("MyTable", pk, val)

and, if it doesn’t have associative arrays, you can emulate them with multiple integer-based arrays of strings.

In our upsert() function, we just constructed a string (update, then insert if the update failed) and passed it to our DBMS. We kept the primary keys separate from our other fields since that made construction of the update statement a lot easier (primary key columns went in the where clause, other columns were just set).

The result of the calls above would result in the following SQL (we had a different check for failed update but I’ve put your @@rowcount in for this example):

update MyTable set
    Name = 'John Brown',
    ItemID = 102
    where ID = 27
if @@rowcount=0
    insert into MyTable (ID, Name, ItemID) values (
        27,
        'John Brown',
        102
    )

That’s one solution which worked well for us. No doubt there are others.