Solved-Lab Assignment 2- Solution

Description

• Preliminaries

Before starting on this assignment, please be sure to read the General Instructions that are on Piazza (under Resources->General Resources). If you did Lab1, you should already know how to log in to the class PostgreSQL server. You’ll get help on Lab2 in your Discussion Section, not the Lectures, so be sure to attend Discussion Sections.

• Goal

The goal of the second assignment is to create a PostgreSQL data schema with 6 tables that are very similar to the tables that you created in Lab1. The tables have the same names, attributes and data types as the tables of Lab1, and the same primary keys but there are some UNIQUE constraints and some restrictions on NULLs.

After you create the data schema with the 6 tables, you will be required to write some SQL statements that use those tables. You have been given data to load into your tables so that you can test the results of your queries. Testing can prove that a query is wrong, but not that it is right, so be careful. Lab2 is due in two weeks, so you will have an opportunity to discuss the assignment during the Discussion Section in the first week of the assignment, and to discuss issues you have had in writing a solution to the assignment during the Discussion Section of the second week. Instructions for submitting the assignment appear at the end of this document.

Lab Assignment 21 CMPS 180 – February 7

• Lab2 Description

3.1 Create PostgreSQL Schema Lab2

You will create a Lab2 schema to set apart the database tables created in this lab from ones you will create in future, as well as from tables (and other objects) in the default (public) schema. Note that the meaning of schema here is specific to PostgreSQL and different from the general meaning. See here for more details on PostgreSQL schemas. You create the Lab2 schema like this:

CREATE SCHEMA Lab2;

Now that you have created the schema, you want to set Lab2 to be your default schema when you use psql. If you do not set Lab2 as the default schema, then you will have to qualify your table names with the schema name (e.g. Lab2.Customers). To set the default schema, you modify your search path. (For more details, see here .)

ALTER ROLE username SET SEARCH_PATH to Lab2;

You do not to have include the CREATE SCHEMA or ALTER ROLE statements in your solution.

3.2 Create tables

You will create tables in schema Lab2 for the tables TaxReturns, Payments, Individuals, Businesses, IRSagents and Delinquents . The attributes of the 6 tables are the same as the tables of Lab1. Data types for the attribute names in these tables are also the same as the ones specified for the tables of Lab1. The primary keys are also the same. In addition, the tables must have the constraints described in the next section.

3.2.1 Constraints

The following attributes cannot be NULL. All other attributes can be (but remember that attributes in Primary Keys also cannot be NULL).

• In Payments: amountPaid

• In TaxReturns: dateFiled

• In IRSAgents: taxpayerID

Also, the following must be unique for the specified table. That is, there cannot be identical rows in that table that have exactly the same (non-NULL) values for all of those attributes (composite unique constraint).

• In Individuals: the attribute spouseID

• In Businesses: the 2 attributes name, address

• In TaxReturns: the 2 attributes taxpayerID, dateFiled

For example, the second constraint says that there can’t be two rows in Business that have the same values for both name and address if both name and address are not NULL.

You will write a CREATE TABLE command for each of the 6 tables. Save the commands in the file create.sql

Lab Assignment 21 CMPS 180 – February 7

4 SQL Queries

Below are English descriptions of the five SQL queries that you need to write for this assignment, which you will include in files queryX.sql, where X is the number of the query, e.g., your SQL statement for Query 1 will be in the file query1.sql and so forth. Follow the directions as given; you will lose points if you give extra tuples or attributes in your results, or if you have missing or wrong results.

4.1 Query 1

Give the different jobLevels that appear for active IRSagents. The jobLevels in your result should appear in decreasing numerical order.

4.2 Query 2

Give the taxPayerID of each business whose name begins with ‘TI’ and that has no tax returns.

4.3 Query 3

For each payment that was made on or after March 1, 2017, give the name and address of the taxpayer who made the payment, the date that the payment was made, and the amount paid. Your result should include both businesses and individuals.

4.4 Query 4

For each individual, the spouseID attribute gives the taxpayerID of that individual’s spouse; it is NULL if the person doesn’t have a spouse. For each individual taxpayer whose spouse is also an individual taxpayer, give the name of both the taxpayer and that taxpayer’s spouse. In your result, the first attribute should be called taxpayerName and the second attribute should be called spouseName.

4.5 Query 5

For each taxpayer that has made one or more payments, give the taxpayerID, the number of payments that the taxpayer made, and the sum of those payments. The 3 attributes in your result should be called payingTaxpayer, howmanyPayments and sumPayments. Your result only includes taxpayers who made at least one payment, so write your query using just the Payments relation.

Lab Assignment 21 CMPS 180 – February 7

5 Testing

While your solution is still a work in progress, it is a good idea to drop all objects from the database every time you run the script, so you can start fresh. Of course, dropping each object may be tedious, and sometimes there may be a particular order in which objects must be dropped. The following commands (which you can put at the top of create.sql if you want, but you don’t have to), will drop your Lab2 schema (and all objects within it), and then create the (empty) schema again:

DROP SCHEMA Lab2 CASCADE;

CREATE SCHEMA Lab2;

Before you submit, login to your database via psql and execute your script. As you’ve learned already, the command to execute a script is: \i <filename>.

Under ResourcesàLab2, we will also give you a load script named lab2_date_loading.sql , that will load data into the 6 tables of the database. (The Delinquents table isn’t used in Lab2, but the other tables are.) You will be able to execute the script with the command:

\i lab2_date_loading.sql.

You should test your 5 queries using that data. (You will have to figure out whether answers are correct on your own.) But you may want to test your SQL statements on your own data as well.

Lab Assignment 21 CMPS 180 – February 7

• Submitting

• 1. Save your scripts for table creations and query statements as create.sql and query1.sql through query5.sql You may add informative comments inside your scripts if you want (the server interprets lines that start with two hyphens as comment lines).

• 2. Zip the file(s) to a single file with name Lab2_XXXXXXX.zip where XXXXXXX is your 7-digit student ID. For example, if a student’s ID is 1234567, then the file that this student submits for Lab2 should be named Lab2_1234567.zip

To generate the zip file you can use the Unix command:

zip Lab2_1234567 create.sql query1.sql query2.sql query3.sql query4.sql query5.sql

(Of course, you use your own student ID, not 1234567.)

3. You should already know how to transfer the files from the UNIX timeshare to your local machine before submitting to Canvas. If you are still not familiar with the process, use the instructions we provided at the Lab1 assignment.

3. Lab2 is due by 11:59pm on Wednesday, February 7. Late submissions will not be accepted, and there will be no make-up Lab assignments.

4. You may lose credit if your queries are unnecessarily complex, even if they are correct. For example, if you use DISTINCT and it’s not necessarily, you may lose half a point. Of course, you could also lose credit if DISTINCT is needed and you omit it.

3. Be sure to follow directions about Academic Integrity that are in the Syllabus and Lecture1. If you have any questions about those directions, please speaker to the instructor as soon as possible.

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