You could take this idea further by fully parsing queries according to the grammar of the SQL language, rather than using simple pattern matching.
In fact it is a result of theoretical computer science that you _cannot_ correctly parse languages like SQL, HTML, Python, etc. with regular expressions: Any attempt to do anything non-trivial will have cases where it misunderstands the code.
So you would want to find a SQL grammar (an outdated example in [1]) and a module[2] that can use this to parse queries into a data structure to which you can apply transformations (e.g., changing case of keyword tokens) and then write back out as a string.
SQLite's documentation has some nice diagrams[3] to get an idea for how it parses a query string. The table of links at the top lets you dive into, e.g., all the optional parts of a SELECT statement.
1: https://ronsavage.github.io/SQL/sql-92.bnf.html
2: https://tomassetti.me/parsing-in-python/
3: https://sqlite.org/lang.html
In fact it is a result of theoretical computer science that you _cannot_ correctly parse languages like SQL, HTML, Python, etc. with regular expressions: Any attempt to do anything non-trivial will have cases where it misunderstands the code.
So you would want to find a SQL grammar (an outdated example in [1]) and a module[2] that can use this to parse queries into a data structure to which you can apply transformations (e.g., changing case of keyword tokens) and then write back out as a string.
SQLite's documentation has some nice diagrams[3] to get an idea for how it parses a query string. The table of links at the top lets you dive into, e.g., all the optional parts of a SELECT statement.
1: https://ronsavage.github.io/SQL/sql-92.bnf.html
2: https://tomassetti.me/parsing-in-python/
3: https://sqlite.org/lang.html