Why this lesson matters

Understand data types and reason about it with a concrete relational example. Relational databases organize durable facts into typed tables, rows and columns. Good type choices make invalid states harder to store and clarify how values can be compared.

How to reason about it

  • For Data Types, the outcome to verify is: Run the statement against sample data and inspect the result before moving to the next case.
  • In Data Types, keep this failure controlled: Choosing text for every field or mixing unrelated entities in one table postpones data-quality problems until queries and reports become unreliable.
  • Data Types practice target: Model a small customer table with suitable types and explain which values are required, optional and unique.

Practical walkthrough

In the Data Types walkthrough: Run the statement against sample data and inspect the result before moving to the next case.

example.sqlsql
CREATE TABLE payments (
  id BIGINT PRIMARY KEY,
  amount DECIMAL(12,2) NOT NULL,
  paid_at TIMESTAMP NULL
);

Practice it yourself

Practice

Data Types exercise

Model a small customer table with suitable types and explain which values are required, optional and unique.

  • Record the expected result before execution
  • Test one valid path and one lesson-specific failure path
  • Explain in two lines which boundary owns the decision

Summary