Python编程调试、代做C++程序设计、c/c++程序语言代写

日期：2021-04-26 11:25

This assignment gives you a brief introduction to connecting to a

database from a program. It will also show you a bit about how You can

write this in either C++, using libpqxx, or in Python, using psycopg2. I

did a solution in Python, which I think is easier.

The assignment:

1. Write 2 programs, one to populate a very simple movie table and one to query that

table.

2. Start by using pgAdmin or psql to create a database called 431hw6

3. For the population program:

1. To help with grading, please use the same schema as in homeworks 1-3. In

your population program, start by creating the schema. As with creating the

movie table below, use the “IF NOT EXISTS” option of the CREATE

SCHEMA command (PostgreSQL: Documentation: 13: CREATE

SCHEMA) so that you can re-run this file without having to manually

remove the schema/table

2. The database to create only has one table called “schema.movie” with the

following fields:

1. title – a varchar field for the title of the movie

2. yr – an int field for the release year of the movie

3. Use a loop to read in some movies and insert them into the table.

4. To get full credit, you do need to use the features of either libpqxx or

psycopg2 to prevent SQL injection attacks (libpqxx: String

escaping or https://www.psycopg.org/docs/sql.html). For the latter, note that

you will be using the sql.Literal() function here since you are replacing

values in the INSERT statement. There is no need to use this feature for the

CREATE statements since those do not include any user input.

5. If you run the program in a CMD/Terminal window, it should look like this:

C:\Users\villa\Downloads\431\sp21>python hw6soln.py

Populating movie database

1

Enter movie title: Nomadland

Enter year of release: 2020

Are you done? (y/n)n

Enter movie title: Da 5 Bloods

Enter year of release: 2020

Are you done? (y/n)n

Enter movie title: First Cow

Enter year of release: 2019

Are you done? (y/n)y

4. For the query program:

1. Use a loop to retrieve results from the table, either searching by title or by

year.

2. You should assume you may get multiple results for either kind of query

3. Gracefully handle the case where you get no results

4. Again, you should protect the query from SQL injection

5. Within the same loop, get a count of the number of movies in the table [We

will use the behavior of these two programs for a discussion of Postgresql’s

concurrency control, and the number of movies might help you understand

the examples better.]

6. Here is sample output if run from a CMD/Terminal window:

C:\Users\villa\Downloads\431\sp21>python hw6bsoln.py

Searching for movies by title or by year

Search for title? (y/n) y

Enter movie title: First Cow

title yr

--------------------

First Cow 2019

Number of movies in database = 3

Are you done? (y/n) n

Search for title? (y/n) n

Enter year of release: 2020

title yr

--------------------

Nomadland 2020

Da 5 Bloods 2020

Number of movies in database = 3

2

Are you done? (y/n) n

Search for title? (y/n) n

Enter year of release: 2021

No results match

Number of movies in database = 3

Are you done? (y/n) y

5. Note on style: it is ok to hard-code a lot here, like the names of the database and user.

You do have to input the values to insert, pick decent variable names and provide some

useful comments.

6. Submit the two programs to Blackboard, either as two .cpp files or as two .py files

Grading:

40% for population program

10% create table

30% insert records from user input

40% for query program

30% searching by title and by year

10% getting number of movies in table

10% properly guard against SQL injection attacks

10% style

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