Programming Interfaces

Psql is ideal for interactively entering SQL commands and for running automated scripts, but it is not ideal for writing applications. Fortunately, POSTGRESQL has interfaces for many programming languages. Programming languages include variables, functions, conditional evaluation, looping, and complex input/output routines, all of which are required for writing good applications.

Table: Interface summary

Interface	Language	Processing	Advantages
LIBPQ	C	compiled	native interface
LIBPGEASY	C	compiled	simplified C
ECPG	C	compiled	ANSI embedded SQL C
LIBPQ++	C++	compiled	object-oriented C
ODBC	ODBC	compiled	application connectivity
JDBC	Java	both	portability
PERL	Perl	interpreted	text processing
PGTCLSH	TCL/TK	interpreted	interfacing, windowing
PYTHON	Python	interpreted	object-oriented
PHP	HTML	interpreted	dynamic Web pages

This chapter will show the same application using each of the interfaces listed in Table

. The application is a very simple one that prompts the user for a United States state code and outputs the state name that goes with the code. Figure

shows the sample application being run. Enter a state code: AL Alabama

For clarity, the text typed by the user appears in bold. The program displays a prompt, the user types AL, and the program displays Alabama. Although state codes are unique, the application is written to allow multiple query return values. The application uses the statename table, which is recreated in Figure

. test=> CREATE TABLE statename (code CHAR(2) PRIMARY KEY, test(> name CHAR(30) test(> ); CREATE test=> INSERT INTO statename VALUES ('AL', 'Alabama'); INSERT 18934 1 test=> INSERT INTO statename VALUES ('AK', 'Alaska'); INSERT 18934 1

Additional information about POSTGRESQL interfaces is available in the Programmer's Manual mentioned in Appendix