Sql representation improvements
Sql representation improvements

Ignore-this: f1bbd37fb6f9bc9db6136312bc976e45

Added a AggrFunSqlExpr value to SqlExpr to represent aggregate functions
vs. other functions. Added two fold functions to fold over SqlSelect
and SqlExpr values.

darcs-hash:20100825211800-447ee-679225ee29d5a6e19b57069b88a3cc67c6a15f64.gz

m4dc4p/haskelldb