Unit notes and practice questions
Everything here is for unit 3 of the Grade 12 Information Technology textbook: what the chapter covers, the short notes, practice questions with their answers, and the lesson video where one exists.
The cards filed under this chapter on the Grade 12 Information Technology page. Open one at a time.
When you use it
Use when updating existing records or removing specific records from a table.
Watch out
Executing UPDATE or DELETE without a WHERE clause affects every single row in the table, permanently overwriting or deleting all data.
Drafted from Grade 12 Information Communication Technology, pages 60-99, then checked twice before it went up
| Category | Commands | Purpose |
|---|---|---|
| DDL | CREATE, ALTER, DROP | Defines and modifies database and table structures. |
| DML | INSERT, UPDATE, DELETE | Manipulates and manages records stored within tables. |
| DQL | SELECT | Queries and retrieves data records from tables. |
When you use it
Use this classification to identify the function of different Structured Query Language statements.
Watch out
Do not confuse DDL commands that alter table structure with DML commands that modify row contents.
Drafted from Grade 12 Information Communication Technology, pages 60-99, then checked twice before it went up
| Clause | Function | Required |
|---|---|---|
| SELECT | Lists the fields to retrieve | Yes |
| FROM | Lists the source tables | Yes |
| WHERE | Filters records based on specified criteria | Optional |
| ORDER BY | Sorts results in ascending (ASC) or descending (DESC) order | Optional |
When you use it
Use when writing queries to retrieve, filter, or sort data from one or more tables.
Watch out
Ascending order (ASC) is the default in ORDER BY. Field names in SELECT must match the table definition exactly.
Drafted from Grade 12 Information Communication Technology, pages 60-99, then checked twice before it went up
When you use it
Use when linking two tables together using CREATE TABLE or ALTER TABLE statements.
Watch out
The foreign key in the child table must have the exact same data type as the primary key it references in the parent table. Always create tables and relationships before populating them with records.
Drafted from Grade 12 Information Communication Technology, pages 60-99, then checked twice before it went up
10 multiple-choice questions written against this chapter, each with its answer and the reason. Try one before you open the answer.
Question 1
In a relational database, what does a single row in a table represent?
Answer: B A record or tuple
Why
In a relational database, each column represents an attribute or field, while each row represents a record (also called a tuple).
Question 2
Which category of SQL commands is used to create, modify, or delete the structure of tables in a database?
Answer: B Data Definition Language (DDL)
Why
Data Definition Language (DDL) contains commands such as CREATE TABLE, ALTER TABLE, and DROP TABLE that define and alter database structures.
Question 3
According to the data types used in MS Access, how much storage size does a Yes/No field occupy?
Answer: A 1 bit
Why
In MS Access, the Yes/No data type holds one of two states (such as Yes/No, True/False, or On/Off) and uses 1 bit of storage.
Question 4
In an SQL SELECT statement, what does the asterisk symbol (*) signify?
Answer: C All columns in the table
Why
When the SELECT keyword is followed by an asterisk (*), it instructs the database to return all columns (fields) from the table.
Question 5
What is the maximum allowable character size for the TEXT data type in MS Access SQL?
Answer: C Up to 63,999 characters
Why
In MS Access, the CHAR data type stores up to 255 characters, whereas the TEXT data type is used for lengthy text and stores up to 63,999 characters.
Question 6
A school administrator in Hawassa executes the following SQL command:
UPDATE Teacher SET T_Salary = 15000;
What is the result of running this command?
Answer: B The salary of all teachers in the table is changed to 15,000 birr.
Why
If the WHERE clause is omitted from an UPDATE statement, the specified modification is applied to every record in the table.
Question 7
Which SQL clause is used to sort query results, and what is its default sorting order?
Answer: C ORDER BY, ascending
Why
The ORDER BY clause specifies how to sort results. Ascending order (ASC) is the default sorting order if neither ASC nor DESC is specified.
Question 8
What is the key difference between the DELETE command and the DROP TABLE command in SQL?
Answer: B DELETE removes data records while keeping the table structure, while DROP TABLE deletes the entire table.
Why
The DELETE command (DML) removes records from a table without destroying the table structure, whereas DROP TABLE (DDL) removes the table and its structure completely.
Question 9
Which SQL command correctly modifies an existing table named COURSE to set C_Department as a foreign key that references D_Number in the DEPARTMENT table?
Answer: A ALTER TABLE COURSE ADD FOREIGN KEY (C_Department) REFERENCES DEPARTMENT (D_Number);
Why
To establish a relationship on an existing table using DDL, the syntax is: ALTER TABLE table_name ADD FOREIGN KEY (column_name) REFERENCES parent_table (primary_key_column);.
Question 10
Consider the following SQL query executed on a SALES table:
SELECT CustomerId, SalesDate FROM SALES WHERE SalesDate BETWEEN '01-01-2020' AND '30-02-2020';
Which records are returned by this query?
Answer: C All sales from 01-01-2020 to 30-02-2020, inclusive of both endpoint dates
Why
The BETWEEN ... AND condition defines a range where both the start point ('01-01-2020') and the end point ('30-02-2020') are included as part of the range.
The app holds 12 questions on this unit, marked as you go. These are the first 10.
Unit 3 runs from page 60 to page 99 of the Ministry of Education edition.
Ministry of Education edition, English, 210 pages
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