Job Ready SQL

Lesson 10Working with SELECT Queries

While understanding DML actions such as inserting, updating, and deleting data is important, the vast majority of work that most people do in a relational database is running queries to retrieve data: the R in CRUD. Even novice developers who are not likely to perform administrative functions in a database should be able to use standard SELECT statements to retrieve data. These statements can also be used in conjunction with programming languages such as Java, C#, and Python, even if the developer never personally connects directly to a database. While you learned a little bit about using SELECT in the previous lesson, in this lesson, you'll dive deeper into its use.

Learning Objectives

By the end of this lesson you will be able to:

• Read data with the SELECT statement
• Filter string, number, and date values in a WHERE clause
• Use the LIKE operator to filter based on a pattern
• Describe the NULL value and strategies for using it

SETTING UP A DATABASE

To effectively learn how to use SELECT, you need to have a database with data that can be retrieved. One possible place to find a database you can use is a consumer complaint dataset from Data.gov (www.data.gov). The Data.gov site includes more than a quarter million open datasets from federal, state, local, and tribal governments. The data is interesting in its own right, but it is also excellent for practice. Without too much trouble, you can import real‐world, meaningful data; decide ...