Using Databases

In this chapter, I will demonstrate how Node.js applications can use a relational database to store and query data. This chapter explains how to work directly with a database by executing SQL queries, and how to take a more hands-off approach with an Object Relational Mapping (ORM) package. Table 12.1 puts this chapter into context.

Table 12.1: Putting databases into context

Question	Answer
What are they?	Databases are the most common means of persistently storing data.
Why are they useful?	Databases can store large volumes of data and enforce a data structure that makes it possible to perform efficient queries.
How are they used?	Databases are managed by database engines, which can be installed as npm packages, run on dedicated servers, or consumed as cloud services.
Are there any pitfalls or limitations?	Databases can be complex and require additional knowledge, such as being able to formulate queries in SQL.
Are there any alternatives?	Databases are not the only way to store data, but they are the most common, and, generally, the most effective because they are robust and scale up easily.

Table 12.2 summarizes what we will do in the chapter.

Table 12.2: Chapter summary

Problem	Solution	Listing
Store data persistently.	Use a database.	7, 8, 12, 13
Simplify the process of changing how data is stored.	Use a repository layer.	9–11
Display stored data.	Include query results when rendering templates.	14, 15
Prevent user-submitted values from being interpreted as SQL.	Use query parameters.	16, 17
Ensure that data is updated consistently.	Use a transaction.	18–21
Use a database without needing to write SQL queries.	Use an ORM package and describe the data used by the application using JavaScript code.	22–25, 27, 28
Perform operations that are too complex to describe using model classes.	Use the ORM package facility for executing SQL.	26
Query for and update data using an ORM.	Use the methods defined by the model classes, with constraints specified using JavaScript objects.	29–32