Build a Practical Schema Design Example in SQL and Relational Databases

Define the build target

For Schema Design, design two related tables or models, add constraints, and create a migration that can be applied to a test database. Build the boundary case using this implementation lens: Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model.

Keep the Schema Design build centered on these technical constraints: Primary keys. Foreign keys and cardinality. Apply them through this path lens: Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model. Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model.

Implement the core behavior

Implement Schema Design around the module artifact—a working schema design example with an explicit success and failure check—and keep the implementation specific to this path context: Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model.

CREATE TABLE customers (
  id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  email text NOT NULL UNIQUE
);

CREATE TABLE orders (
  id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  customer_id bigint NOT NULL REFERENCES customers(id),
  total numeric(10,2) NOT NULL CHECK (total >= 0)
);

psql -f schema.sql

The database rejects duplicate customer emails, missing customers, and negative order totals.

practice/\n├── README.md\n├── schema-design-build.sql\n└── evidence/\n    └── expected-result.txt

Run the complete path

Run one realistic Schema Design case end to end and record the required evidence: the relevant output, test, log, query result, or rendered state for Schema Design. Interpret the result through this path context: Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model.

Change one meaningful condition

Modify one condition central to Schema Design using this path context: Use relational tables, keys, transactions, SQL result sets, constraints, query plans, and database state as the concrete model. Predict the new result before rerunning the same workflow.

Verify the artifact

Your deliverable is a working schema design example with an explicit success and failure check.

Common mistakes to avoid

• Relationship cardinality wrong.
• Constraint missing from database.
• Destructive migration without backfill.
• Duplicate data violates new constraint.