What We Cover in Database Assignments
- Conceptual design: entity-relationship diagrams in Chen or crow's foot notation, with cardinality and participation.
- Logical design: mapping ER models to relations, choosing primary and foreign keys.
- Normalisation: functional dependencies and moving data to 1NF, 2NF, 3NF and BCNF, with the reasoning shown.
- SQL DDL and DML: CREATE, ALTER, INSERT, UPDATE and DELETE with constraints.
- Queries: joins, subqueries, GROUP BY and HAVING, window functions and views.
- Procedural SQL: stored procedures, functions and triggers in PL/SQL, T-SQL or PL/pgSQL.
- Performance: indexes, query plans and transactions with isolation levels.
- NoSQL: MongoDB document design and aggregation pipelines.
From Case Study to Working Database
Most database assignments begin with a scenario: a clinic, a car rental company, a university enrolment system. Your specialist reads it closely and lists the business rules hidden in the text, such as "each booking belongs to exactly one customer". Those rules decide the entities, relationships and constraints.
Next, the ER diagram is drawn and checked against every rule. The model is then converted to tables and normalised, with a short explanation for each step so you can show your working. Finally, the specialist writes the scripts to create the schema, inserts realistic sample data and writes each query your brief asks for, together with the output.
Getting Queries Right
SQL questions are often marked on exact output, so precision matters. Our specialists test every query against the sample data and think about tricky cases: customers with no orders, ties in a ranking, NULL values in a calculation. Where there are several correct approaches, such as a join or a subquery, they choose the clearer one and mention the alternative.
Common sticking points
- Outer joins that drop rows unexpectedly.
- Aggregates mixed with non-grouped columns.
- Correlated subqueries that are hard to read.
- Date handling that differs between MySQL, Oracle and SQL Server.
Database Systems We Use
We work in the system your unit uses, including MySQL, PostgreSQL, Oracle, Microsoft SQL Server, SQLite and MongoDB. Syntax differs between them, so tell us which one your marker will use. The PostgreSQL tutorial is a good free reference for core SQL concepts, whichever system you study.
Reports and Documentation
Many units ask for a written design report: assumptions, the ER diagram, a data dictionary and justification for normalisation decisions. Your specialist writes this so it matches the delivered database exactly, using the diagramming tool your unit names.
Database Design Mistakes to Avoid
Most lost marks in database assignments come from the design stage. Storing several values in one column, such as a list of phone numbers, breaks first normal form. Using a name or email as a primary key causes trouble when it changes. Forgetting to model a many-to-many relationship with a bridging table leads to duplicated data. Leaving out constraints means the database will happily accept a booking for a customer who does not exist.
Query mistakes are usually about logic rather than syntax. An inner join quietly drops customers without orders. A COUNT on the wrong column counts NULLs differently from what you expect. A GROUP BY that leaves out a selected column fails in PostgreSQL but runs in older MySQL settings with misleading results.
Our specialists avoid these problems and explain each one in the notes that come with your solution. That way the delivered database is correct, and you also learn the patterns that make your own future designs stronger.
Learning From the Solution
Run the scripts on your own machine, then try writing a new query before looking at ours. Comparing your approach with a worked solution is one of the quickest ways to improve at SQL. Please use our work as a reference, in line with our fair use policy.
Price and Turnaround
A set of queries on an existing database can often be done in a day. Full design projects with a report usually need three to five days. You get a fixed quote within 30 minutes, and changes are free for 15 days.