Can someone please explain to a newbie when I need to use quotes with variables in my sql statements?

I've seen code with " & variable & " like the example below...what does this mean?

Thanks

"INSERT INTO linkToCategory(ein, categoryId) " & _
"VALUES (" & EIN & ", " & selectedGroup &")"

You always need to use this " & variable & " syntax. This is because you want to embed the value of the variable into the SQL statement. If you don't use this syntax, you will be embedding the name of the variable instead.

Using your SQL statement as an example, suppose you have:
EIN = 1
selectedGroup = 2

then if you do:
"INSERT INTO linkToCategory(ein, categoryId) " & _
"VALUES (" & EIN & ", " & selectedGroup &")"

that gives you this SQL statement:
which is what you want.

If you don't use the " & variable & " syntax then you have:
"INSERT INTO linkToCategory(ein, categoryId) " & _
"VALUES (EIN, selectedGroup)"

which gives this SQL statement:
and you don't want that because the database will assume that EIN and selectedGroup are the actual values you're trying to insert. The database will not know that EIN and selectedGroup are variables in your code that contain the values you want to insert.

hth
Phil