Actually it's still ambiguous, because you forgot about sub-expressions. How would you parse this: SELECT a as aliasA b select q from foo as aliasQ c as ali

Actually it's still ambiguous, because you forgot about sub-expressions. How would you parse this: SELECT a as aliasA b select q from foo as aliasQ c as aliasC FROM d as aliasD e Even if you can figure it out (and add a 3rd level of sub-expression before deciding if you can), it's completely unreadable. You need either commas or parenthesis.