Have you thought about JSON as a partial query placeholder, and all the native methods available for traversal, merging, plucking, etc.?

For example, here is :

{ type: 'select', columns: [{ expression: 'orgJobs.org_job_code', alias: 'job_code' }], joins: [{ table: 'org_jobs', alias: 'orgJobs' }], limit: 100, offset: 0 }

which yields:

select orgJobs.org_job_code as job_code from org_jobs as orgJobs limit 100 offset 0

and so its easy to do things like:

query.limit = 100;

and of course:

query.columns.push(additionalColumn);

and use something like lodash/underscore (or equivalent for your language) to add collection/array/object helper methods so you never have to write for-loops for things like mapping and property plucking.