Module Dbi

module Dbi: sig .. end

Generic database interface.

Making a connection to a specific type of database:

  module DB = Dbi_postgres

  let dbh = new DB.connection "database_name"

Simple usage, returning one row:

  let sth = dbh#prepare "SELECT name FROM employees WHERE empid = ?" in

  sth#execute [`Int 100];

  let [`String name] = sth#fetch1 in ...

Simple usage, returning multiple rows:

  let sth = dbh#prepare "SELECT firstname, name FROM employees\n                         WHERE salary > ?" in

  sth#execute [`Int 10000];

  sth#iter(function

           | [(`Null | `String _) as fname, `String name] ->

               do_something_with fname name

           | _ -> assert false);

Advanced usage, reusing prepared statements:

  let sth =

    dbh#prepare "INSERT INTO employees(name, salary) VALUES (?, ?)" in

  List.iter(fun (name, salary) ->

              sth#execute [`String name; `Int salary];

              let id = sth#serial "" in

              Printf.printf "Employee %s has been assigned ID %d\n" name id

           ) employees_list;

Caml mappings of SQL types.

type date = {

	`year : int;`
	`month : int;`
	`day : int;`

}
type time = {

	`hour : int;`
	`min : int;`
	`sec : int;`
	`microsec : int;`
	`timezone : int option;`

}

type datetime = date * time

module Decimal: sig .. end

type sql_t = [ `Bigint of Big_int.big_int
       | `Binary of string
       | `Bool of bool
       | `Date of date
       | `Decimal of Decimal.t
       | `Float of float
       | `Int of int
       | `Interval of datetime
       | `Null
       | `String of string
       | `Time of time
       | `Timestamp of datetime
       | `Unknown of string ]

val sql_t_to_string : sql_t -> string

sql_t_to_string t returns a string representation of t following the Ocaml conventions. The aim is to offer an easy way to print sql_t values.

val sdebug : sql_t list -> string

sdebug ss can be used to debug the return value from a #fetch1, #map or other query. It converts the sql_t list type into a printable form which may be printed on stderr to aid in debugging the actual types returned by the database.

val intoption : int option -> sql_t

intoption(Some i) returns `Int i and intoption None returns `Null.

val stringoption : string option -> sql_t

stringoption(Some s) returns `String s and stringoption None returns `Null.

type precommit_handle

See Dbi.connection.register_precommit.

type postrollback_handle

See Dbi.connection.register_postrollback.

SQL utility functions.

val string_escaped : string -> string

escape_string s escapes the string s according to SQL rules and surrounds it with single quotes. This should be hardly needed as the data provided through the sql_t types will automatically be escaped for you.

val placeholders : int -> string

placeholders n returns a string of the form "(?, ?, ..., ?)" containing n question marks.
Raises Invalid_argument if n <= 0.

exception SQL_error of string

Exceptions thrown by subclasses on SQL errors.

class virtual statement : connection -> object .. end

class virtual connection : ?host:string -> ?port:string -> ?user:string -> ?password:string -> string -> object .. end