Download pyPgSQL Examples

pyPgSQL Examples
By: Benjamin Arai & Conley Read
Summary
 Code Snippet
 Insertion Example
 Deletion Example
 Selection Example
Code Snippet
This code snippet is an example of creating a connection and an execution of a query using pyPgSQL. The connection manager function can
specify other parameters, which include username and password. All of the source code and queries are assuming the database is PostgreSQL
7.4.1 and Python is version 2.3.3. The pyPgSQL package is not currently installed on any of the lab computers, but is installed on
hebe.cs.ucr.edu.
from pyPgSQL import PgSQL
cx = PgSQL.connect(database=”db_name”)
cx.execute(“QUERY”)
cx.close()
The connection example does not cover SQL commands you would need to do in-order for locking or transactions on the database but it is in
most cases it is usually only a additional two or three executions of starting and stopping the task.
Insertion Example
This is an insertion into the QuestionVersions table and assumes there is no foreign linking between tables. There are also ALTER queries that
can be used to modify data in the database.
“Integer”,
“Integer”,
“Integer”,
“Boolean”,
“Text”,
“Text”,
“Text”,
“Text”,
“Text”,
“Double”,
“Text”
);
INSERT INTO QuestionVersions VALUES(
Integer
Boolean
= 32-bit integer number.
= Can be represented as a 0/1 or true/false value.
Text
Double
= Text string of variable size.
= Double precision number.
Deletion Example
This is an example of a deletion using the ProfessorID as the only parameter for deletion. The parameter specified for the column most
correspond with the type specified in the database.
DELETE FROM QuestionVersions WHERE ProfessorID=”Integer”;
The ProfessorID is the column from which the query will make the decision on what to delete. Multiple columns can be used after the
WHERE CLAUSE to refine and/or widen a search.
Selection Example
This is a select using the Statement field to find all of the questions that contain the word “tree”.
SELECT * FROM QuestionVersions WHERE Statement LIKE %Text%;
The “%” sign is a wild card for 0 or more items. The “%” sign can be replaced with a “$”, which represents exactly one character wild card
value and can be specified multiple times in a query.
Other Stuff
These are all simple examples that can be extended to include multiple columns, sub queries and etc. Advanced topics including server-side
includes and triggers are covered in the PostgreSQL documentation.