Lab 0: An Introduction to SQL¶

SQL is a programming language often used to work with data, particularly data structured as a table. It can be used to find all rows in a table that satisfy a condition, or “query” the table. It’s also used to manipulate a table, by inserting, modifying, or deleting rows.

Because SQL is used extensively in industry, it’s useful to have been exposed to it if you’re looking for an internship working with data.

SQL acts differently to Python or other languages you may have learned before. In Python, you tell the computer each step to take to get the result you want. In SQL, you tell the computer the result you want and it takes the steps itself.

Suppose we have a list of items, each of which has some weight (measured in pounds). Now suppose we want to find all of the items that weigh more than 10 pounds.

In Python, you tend to work with one item at a time. So we might use a for loop over all the items to check whether the weight is more than 10. We start with a list containing our items.

>>> items = [item1, item2, item3]
>>> item1.weight = 15
>>> item2.weight = 5
>>> item3.weight = 20

heavy_items = []
for item in items:
   if item.weight > 10:
   heavy_items.append(item)

>>> heavy_items
[item1, item3]

SQL, however, is optimized for sets. So we would solve the problem by asking SQL to give us the subset where the weight is more than 10. Instead of a list, SQL stores data in a table.

items¶
Name	Weight
item1	15
item2	5
item3	20

SELECT * FROM items WHERE Weight > 10

Name	Weight
item1	15
item3	20

In this lab, we will give you a brief introduction to SQL. Visit

https://sqlbolt.com/lesson/introduction

Start by reading the instructions in the Introduction.

Task 1¶

Complete every exercise from each of the following lessons:

Lesson 1: SELECT queries 101
Lesson 2: Queries with constraints (Pt. 1)
Lesson 3: Queries with constraints (Pt. 2)
Lesson 4: Filtering and sorting Query results
Review: Simple SELECT Queries
Lesson 6: Multi-table queries with JOINs