◊(Local Yarn Code "Diff")

already holds an active connection, it will be @racket[disconnect]ed and then replaced with the new
connection.

@defproc[(query! [query-statement statement?] [parameters any/c] ...) void?]

Executes a SQL statement using the current connection.

@defproc*[([(select-rows! [query statement?] [fieldnames (listof stringish?)]) hash?]
@defproc*[([(select-rows! [query statement?] [fieldnames (listof stringish?)]) (listof hash?)]
           [(select-rows! [table stringish?] [fieldnames (listof stringish?)] [where-clause
              stringish?]) hash?])]
              stringish?]) (listof hash?)])]

Execute a SQL query that returns rows from the database, either using a raw query (first form
above), or using a table name, field names, and a @racket[_where-clause] (second form above).
Returns a hash table whose keys are the field names supplied.
Returns a list of hashes whose keys are the values supplied in @racket[_fieldnames].

In the first form, @racket[_fieldnames] should list all the fields that will be returned by the
query, in order, since this list will be used as the keys for the hash table result.
In the first form, @racket[_fieldnames] should list @emph{in order} all the fields that will be
returned by the query. If this isn’t done, the keys for each row’s hash will likely point to values
for the wrong fields.