The SELECT statement is the most important SQL command in IB Computer Science. It allows users to retrieve specific data from a database, turning stored records into useful information. In IB exams, students are often asked to write, interpret, or modify SELECT queries, so understanding how they work step by step is essential.
Examiners reward clarity of logic more than perfect syntax.
What Is a SELECT Query?
A SELECT query is used to:
- Retrieve data from a database table
- Choose specific fields
- Filter records
- Control how results are displayed
It does not change the data — it only reads it.
In IB terms, SELECT is used for data retrieval.
Basic Structure of a SELECT Query
A simple SELECT query follows this structure:
- SELECT field(s)
- FROM table
This tells the database:
- What data you want
- Where to find it
For example, selecting student names from a student table retrieves only that specific information, not the entire record.
Selecting All Fields
To retrieve all fields from a table, the wildcard symbol is used.
This tells the database:
- Return every column
- For every matching record
IB students should understand that:
- This is convenient
- But often inefficient in large databases
Examiners may reward students who select only the fields they need.
Selecting Specific Fields
To retrieve only certain fields:
- List the field names after SELECT
- Separate multiple fields with commas
This allows:
- Cleaner results
- Faster queries
- More precise data access
Using specific fields demonstrates good database practice.
Filtering Records with WHERE
The WHERE clause filters records based on conditions.
It allows the query to:
- Return only records that meet criteria
- Exclude unwanted data
For example, a WHERE condition can:
- Select students in a specific year group
- Retrieve records with a certain value
IB students should understand that:
- WHERE applies conditions
- Only matching records are returned
Using Comparison Operators
WHERE conditions often use:
- Equals
- Greater than
- Less than
These operators allow numerical and text-based filtering.
Clear explanation of how conditions limit results is more important than memorising symbols.
Sorting Results with ORDER BY
The ORDER BY clause controls the order of results.
It can:
- Sort data alphabetically
- Sort data numerically
- Sort in ascending or descending order
This affects how results are displayed, not which records are selected.
How SELECT Queries Appear in IB Exams
IB exam questions may ask students to:
- Write a SELECT query for a scenario
- Explain what a given query does
- Modify a query to meet new conditions
- Identify errors in a query
Step-by-step explanations score higher than copying syntax.
Common Student Mistakes
Students often:
- Forget the FROM clause
- Confuse fields and tables
- Apply WHERE after ORDER BY
- Use vague explanations
Understanding the role of each clause is essential.
Why SELECT Queries Matter
SELECT queries are used in:
- School databases
- Banking systems
- Websites
- Data analysis tools
They are the foundation of how data is accessed in real-world systems.
Final Thoughts
The SELECT statement allows users to retrieve exactly the data they need from a database. By choosing fields, filtering records, and ordering results, SQL turns raw data into meaningful information.
Mastering SELECT queries gives IB Computer Science students the skills needed to understand database questions clearly and confidently — exactly what examiners expect.
