On Wed, Jul 1, 2009 at 5:29 PM, Rick Ratchford<[email protected]> wrote:
> 1. Determine if the table has already been created due to a prior run.
>
> 2. If so, to remove the information currently in that table and replace it
> with new information.
>
> I'm not sure how to determine whether the table already exists.
>
> If it does exist, I suppose I can then use the SQL Delete to delete all the
> records and then write the new stuff. If this is not the way to do it, maybe
> someone can suggest the proper way.
Well, here are a few commands that may give you some ideas, and you
can see what works best for you....
Here is how you can use sqlite_master to determine if a table exists:
SELECT count(*) FROM sqlite_master WHERE tbl_name = 'Foo';
-- returns 1 if table exists, 0 otherwise
If you want to drop your table and then create it, you could do this:
DROP TABLE Foo;
-- It's okay to execute this command, even if Foo does not exist already.
CREATE TABLE Foo ( ... );
Here you can see whether or not a table contains any rows at all:
SELECT count(*) FROM Foo;
-- returns 0 if table is empty
If you want to clean out your table:
DELETE FROM Foo;
-- This will delete all rows from Foo
If you just want to update some already existing data:
UPDATE Foo SET column2 = 33 WHERE column1 = 1;
-- This lets you update (modify) information that already exists
in the table
-David
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