Question

I have column in a postgresql database. They are lottery numbers. Four digits in length to be exact. Initially I had the datatype of the column as int. I inserted all the lottery numbers. After I inserted all the numbers I realize it chopped off my zeros. For instance 0925 is 925. I fixed the datatype to be varchar but now I need to figure out how to fix it from int to varchar with the same data. The data needs to be 4 digits in length. I was trying to just figure out how many problem numbers there are and I couldn’t write a select statement that told me how many rows have less than 4 digits.

How should I go about this?

Thanks.

Answer 1

I was trying to just figure out how many problem numbers there are and I couldn’t write a select statement that told me how many rows have less than 4 digits.

SELECT COUNT(*)
FROM lottery
WHERE char_length(x) < 4

See it working online: sqlfiddle

To fix them, you may find lpad useful. Note that the WHERE clause is not actually needed.

UPDATE lottery
SET x = lpad(x, 4, '0')

See it working online: sqlfiddle