Identify which part of the query columns are a part of

[smaspe]

I'd like to be able to identify which part of the query columns belong to.

For example, in

SELECT foo FROM bar WHERE baz = 1

get_query_columns will return ["foo", "baz"]

I think it would be useful to know that "foo" is part of the projection, while "baz" is part of the WHERE clause.

Since get_query_columns keep track of the keyword the column belongs too (https://github.com/macbre/sql-metadata/blob/master/sql_metadata.py#L132), it should be possible to associate the column to it's query part.

[macbre]

@smaspe - great idea, thanks for reporting!