SQL: Allow "AS" table alias expressions

[ukclivecox]

Is your feature request related to a problem?

Example:

import daft

df = daft.from_pydict({"a": [0, 2, 3, 11, 12]})

daft.sql("select * from df where df.a > 3").show()

daft.sql("select * from df as foo where foo.a > 3").show()

The first sql works but the second gives a Table not found: foo exception

Describe the solution you'd like

Support schema.table AS identifier expressions. Most SQL also allows AS to be optional: see here and for postgres

Describe alternatives you've considered

In my case the SQL is autogenerated so would need some effort to remove table aliases where ever they can be used.

Additional Context

version 0.3.8

Would you like to implement a fix?

Yes