datas.json

{
    "mahasiswa": [
        "nim",
        "nama",
        "alamat",
        "ipk"
    ],
    "matakuliah": [
        "kode",
        "nama",
        "sks"
    ],
    "registrasi": [
        "nim",
        "kode",
        "semester",
        "tahun_ajar",
        "nilai"
    ]
}

parser.py

import json

## dataset
with open('datas.json') as f:
	datas = json.load(f)

## helper
parser = lambda x, y, z = '': x[x.find(y) + len(y) + 0x01:x.find(z) - 0x01]
error  = lambda x: exit('SQL Error (Missing ;)' if not x else 'SQL Error (Syntax Error) || Reason: {}'.format(x))

## input
_ = "SELECT m.nim,nama,kode,nilai FROM mahasiswa m JOIN registrasi r ON (m.nim=r.nim);".lower()

if _[-1] != ';': error(None)

tables, alias = parser(_, 'from', 'join').split()
if tables not in datas:
	error('tables [{}] not found !!'.format(tables))

print 'Table Main: {} -> {}'.format(tables, alias)

columns, ct = parser(_, 'select', 'from').split(','), []
for c in columns:
	if '{}.'.format(alias) in c:
		temp = c.split('.')[1]
		if temp not in datas[tables]:
			error('columns [{}] not found !!'.format(temp))
		else:
			ct.append(temp)

for c in columns:
	if c in datas[tables] and c not in ct:
		ct.append(c)

print 'List Kolom: {}'.format(', '.join(ct))

## extend (JOIN Query)
if 'join' in _:
	tables, alias = parser(_, 'join', 'on').split()
	print 'Table Join: {} -> {}'.format(tables, alias)

	condition, ct = parser(_, 'on')[1:-1], []
	for c in condition.split('='):
		if '{}.'.format(alias) in c:
			ct.append(c.split('.')[1])

	for c in columns:
		if c in datas[tables]:
			ct.append(c)

	print 'List Kolom: {}'.format(', '.join(ct))