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110 lines
3.7 KiB
110 lines
3.7 KiB
# SQL Practise
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### Learning Objectives
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1. Practice creating a database from the command line
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2. Practice creating an SQL schema
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3. Practise seeding an SQL database
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4. Practice querying a database using SQL
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#1. CREATION
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- Open up the psql server by typing `psql` in terminal
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- Make a database called 'realty' with `CREATE DATABASE realty;`
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- You can check if this has worked by typing `\l`, and you will get a list of your databases
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- Exit the psql server with `\q`
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#2. SCHEMA
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In your homework folder, touch an SQL file called `schema.sql`. Create a schema based off the following ERD.
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Note: VARCHAR is a text type that is character-limited, typically up to 255.
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(See below for create table SQL syntax).
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- apartments should have:
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- id - serial primary key
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- tenant - varchar
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- offices should have:
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- id - serial primary key
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- sq_ft - integer
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- cubicles - integer
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- bathrooms - integer
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- company - varchar
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- storefronts should have:
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- kitchen - boolean
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- sq_ft - integer
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- outdoor_seating - boolean
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Your create table syntax will look something like:
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```
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CREATE TABLE apartments (
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id SERIAL PRIMARY KEY,
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tenant VARCHAR(255)
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);
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```
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Etc. You can create multiple tables in the same .sql file.
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From the command line load the schema `schema.sql` into the database:
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- Go into the directory where `schema.sql` is located.
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- In terminal, NOT in the the psql server, type `psql -d realty < schema.sql`
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This tells the database (-d) called realty to 'eat' the contents of schema.sql.
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You can check if this has worked by going into your psql server and connecting
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to the realty database with `\c realty`. The `\c` command is used to connect to any database you have stored in psql.
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Now type `\dt` and you should see a list of the tables you have created.
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To see a list of your columns in a table, for example the apartment table, type `SELECT * FROM apartments`
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Quit psql again with `\q`
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#3. SEED
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- Create a new file called `seed.sql`, and in this file you should
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- **Practise writing the proper INSERT commands that will add new entries into your apartment, office and storefront tables.** You should create at least 3 entries for each table. Vary the attributes of each entry so no two are alike.
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</br>
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- From the command line, load this seed file into your database. In the directory where your seed file is located, type the same command as before but substitute the
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schema.sql for seed.sql: `psql -d realty < seed.sql`. You should see a list of INSERTs.
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#4. CRUD
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Perform these operations from the `psql` command line
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- Practice editing tables
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- Change the tenant of an apartment
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- Change the number of bathrooms in an office
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- Practice deleting entries
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- delete the storefront with the lowest square footage
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- delete the office with the most cubicles
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- Practise more inserts
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- add a storefront that has outdoor seating
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- add an office with ten bathrooms
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#5. QUERIES
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Create a new markdown file `realty.md` and write the SQL commands you would use to retrieve the following information from your database. Test each command in PSQL to make sure it is correct:
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- The average square footage of all offices
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- The total number of apartments
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- The apartments where there is no tenant
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- The names of all of the companies
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- The number of cubicles and bathrooms in the 3rd office
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- The storefronts that have kitchens
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- The storefront with the highest square footage and outdoor seating
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- The office with the lowest number of cubicles
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- The office with the most cubicles and bathrooms combined
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W3 schools has good guides for sql commands along the left sidebar: http://www.w3schools.com/sql/default.asp
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