A representation of a query string to send to a database, abstracting over parameter references and providing nested concatenation to simplify generation. For databases which only support linear parameters (typically denoted "?"), the driver will reshuffle, elide, and duplicate parameters as needed.

normal q rewrites q to a normal form containing at most one top-level S constructor, containing no empty literals, and no consecutive literals. This function can be used to post-process queries before using equal and hash.

Equality predicate for query.

A hash function compatible with equal. This is currently Hashtbl.hash.

pp ppf q prints a human-readable representation of q on ppf. The printed string is not suitable for sending to an SQL database; doing so may lead to an SQL injection vulnerability.

show q is the same human-readable representation of q as printed by pp. The returned string is not suitable for sending to an SQL database; doing so may lead to an SQL injection vulnerability.

concat sep frags is frags interfixed with sep if frags is non-empty and the empty string of frags is empty.