How to add a new column with existing and new rows to a table? - sql

Question

I have a table that I created with a unique key and each other column representing one day of December 2014 (eg named D20141226 for data from 26/12/2014). So the table consists of 32 columns (key + 31 days). These daily columns are indicating that a customer had a transaction on that specific day or no transaction is indicated by a 0.
Now I want to execute the same query on a daily basis, producing a list of unique keys that had a transaction on that specific day. I used this easy script:
CREATE TABLE C01012015 AS
SELECT DISTINCT CALLING_ISDN AS A_PARTY
FROM CDRICC_012015
WHERE CALL_STA_TIME ::date = '2015-01-01'
Now my question is, how can I add the content of the new daily table to the existing table with the 31 days, making it effectively a table with 32 days of data (and then continue to do so on a daily basis to store up to 360 days of data)?
Please note that new customer are doing transactions every day hence there will unique keys in the daily table that aren't in the big table holding all the previous days.
It would be ideal if those new rows would automatically get a 0 instead of a NULL but I can work around it if it gets a NULL value (not sure how to make sure it gets a 0 instead).
I thought that a FULL OUTER JOIN would be the solution but that would mean that I have to list all variables in the select statement, which becomes quite large as I add one more column each day. Is there a more elegant way to do this?
Or is SQL just not suited to this and a programming language like eg R would be much better at this?

Answer 1

If you have the option to change your schema completely, you should unpivot your table so that your columns are something like CUSTOMER_ID INTEGER, D DATE, DID_TRANSACTION BOOLEAN. There's a post on the Enzee Community website that suggests using a user-defined table function (UDTF) to do this. If you change your schema in this way, a simple insert will work just fine and there will be no need to add columns dynamically.
If you can't change your schema that much but you're still able to add columns, you could add a column for every day of the year up front with a default value of FALSE (assuming it's a boolean column representing whether the customer had a transaction or not on that day). You probably want to script this.
ALTER TABLE table_with_daily_columns MODIFY COLUMN (D20140101 BOOLEAN DEFAULT FALSE);
ALTER TABLE table_with_daily_columns MODIFY COLUMN (D20140102 BOOLEAN DEFAULT FALSE);
-- etc
ALTER TABLE table_with_daily_columns ADD COLUMN (D20150101 BOOLEAN DEFAULT FALSE);
GROOM TABLE table_with_daily_columns;
When you alter a table like this, Netezza creates a new table and an internal view that does a UNION of the new table and the old. You need to GROOM the table to merge the tables back into a single one for improved performance.
If you really must keep one column per day, then you'll have to use the method you described to pivot the data from your daily transaction table. Set the default value for each of your columns to 0 or FALSE as described above, then:
INSERT INTO table_with_daily_columns
SELECT
cust_id,
TRUE as D20150101
FROM C01012015;