PostgreSQL Database

• a PostgreSQL server instance manage a database cluster
• a database cluster consists of a collection of database
• tables are grouped into a database.
• each table is a named collection of rows
• each row of a table has a fixed order of named columns
• each column is of a specific data type

Window Function

SELECT user, department, salary, 
  avg(salary) OVER (PARTITION BY department) 
FROM empsalary;

PL/Tcl

Use Tcl language to write PostgreSQL functions and procedures.

Tcl code is executed in a safe Tcl interpreter.

CREATE FUNCTION
  tcl_max (integer, interger) RETURNS integer
AS $$
  if {$1 > $2} { return $1}
  return $2  
$$ LANGUAGE pltcl

Table Joins

• INNER JOIN
• LEFT OUTER JOIN
• RIGHT OUTER JOIN
• FULL Outer JOIN