Select same account numbers in a new table - sql

Question

Using Teradata SQL Assistant, I want to be able to pull a table a year ahead but only the ones that would match the results in the query from the year before. Here's what I am trying to do. I pulled a table that contains information where the results in a specific column equals 0 for no. I want to pull information from 1 year ahead where the results in that column equals 1 but only include the account numbers that came when I pulled the results for the year before. Like only pull the customer account numbers for the year ahead that are the same from the year before.
Explanation: I pull the one table that has 0 in the column. From that, I want to see which of those accounts became a 1 in the table from a year ahead. The table has millions of accounts and I just have my settings for 10,000 of them so I want to see of those 10,000 in the first year that did not have the product, how many of them became 1 in the second year.
Can I do this? If so, how? I have been googling and I do not think I am explaining what I am trying to do correctly in my google query so I am coming up short with results.

Answer 1

Thanks for clarifying. That makes it a little simpler. I would put the second year data in a subquery and filter the main table on the first year and quantity = 0. This will give you two columns one with the first year and one with the second year. If you're only looking for this information for a single product_id you will need to add this to both WHERE clauses.
SELECT TABLE_NAME.ACCOUNT_ID, TABLE_NAME.QUANTITY AS "2019" , YEAR_TWO.QUANTITY AS "2020"
FROM TABLE_NAME
LEFT JOIN
(
SELECT *
FROM TABLE
WHERE YEAR = 2020
) YEAR_TWO ON TABLE_NAME.ACCOUNT_ID = YEAR_TWO.ACCOUNT_ID
WHERE TABLE_NAME.YEAR = 2019
AND TABLE_NAME.QUANTITY = 0
If you want just the % of accounts that are no longer 0 in the second year you could try something like this (adding up all the 1s and dividing by total count)
SELECT TABLE_NAME.YEAR, SUM(YEAR_TWO.QUANTITY) / COUNT(YEAR_TWO.QUANTITY) AS PERCENTAGE_NOT_ZERO
FROM TABLE_NAME
LEFT JOIN
(
SELECT *
FROM TABLE
WHERE YEAR = 2020
) YEAR_TWO ON TABLE_NAME.ACCOUNT_ID = YEAR_TWO.ACCOUNT_ID
WHERE TABLE_NAME.YEAR = 2019
AND TABLE_NAME.QUANTITY = 0
GROUP BY TABLE_NAME.YEAR