Finally, all letters were removed from the data, resulting in the final version of ptoproperty_cleaned.
The ptoproperty_cleaned table contains application numbers, publication numbers, and patent numbers. The patents may also have two distinct publication numbers based on the year in which it was published. Based on length of documentid, the three types of id numbers were separated into three separate tables.
DROP TABLE ptoproperty_patent;
SELECT * FROM ptoproperty_cleaned WHERE length(documentid) = 7;
--8696149
ALTER TABLE ptoproperty_patent RENAME COLUMN documentid TO patentno;