Sumita Arora Solution

Site-package is the folder and default place from where python interpreter import all user defined packages and library. So to import any package using import command we must attach it to site-package folder of Python Installation.

Without __init__.py Python will not be able to find sub-modules inside package directory and so attempt to import module fails.

Library is collection of packages. Library is similar to directory in system Steps to create own library in python- Decide basic structure of package like name of package, module, sub-folders, sub-packages which will be part of it. Create the directory structure including folders, package name, sub packages. Inside main package folder create file/module i.e. .py

Package is collection of modules stored as a directory under a common name space. Similar to folder in a directory A special file _init_.py must be included in package

Docstring are comment quoted with triple quotation marks. Used within a program for documentation. Docstring have no effect during program execution Displayed as document when help (modulename) command is issued. Example

Modules are independent set of code and data stored as individual components. Modules can be included in any program without having to rewrite them. The extension of python module is .py Advantages Code reusability Reduce complexity

Aggregate functions work with multiple rows of table at a time and return single aggregate value. It is basically used to produce summarized data from our database. Basically there are five aggregate functions:– COUNT()– AVG()– MIN()– MAX()– SUM() ExamplesSELECT SUM(Total) FROM ITEM; SELECT AVG(Marks) FROM Student; SELECT DeptNo, MAX(Salary)FROM EmployeeGROUP BY DeptNo;

The GROUP BY clause combines all those records that have identical value in a particular field or a group of fields. SELECT ItemName, Sum(QtySold)FROM OrderWHERE OrderDate = current_date()GROUP BY ItemName;

WHERE Cluase HAVING Clause It is implemented in row operations It is implemented in column operations It is applied to single row It is applied to summerized rows or groups Aggregate functions can not be used Can use Aggregate functions Can be used with SELECT, UPDATE, DELETE statements Can only be used with SELECT statements

ORDER BY clause used to arrange the result set of query in ascending or descending order in order of single or multiple columns. ORDER BY clause is used in conjuction with SELECT statement. SELECT <field name(s)>FROM <table name>WHERE <condition>ORDER BY <field name> [ASC | DESC]; Example:SELECT * FROM EmployeeORDER BY empname;