Why stored procedures centralize logic in MySQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a stored procedure that selects all rows from the employees table.

MySQL

CREATE PROCEDURE GetAllEmployees() BEGIN SELECT * FROM [1]; END;

Drag options to blanks, or click blank then click option'

Asalaries

Bdepartments

Cemployees

Dprojects

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a table unrelated to employees like departments or projects.

Forgetting to specify the table name.

The stored procedure should select from the employees table to retrieve all employee records.

2fill in blank

medium

Complete the code to call the stored procedure named GetAllEmployees.

MySQL

CALL [1]();

Drag options to blanks, or click blank then click option'

AGetAllEmployees

BSelectEmployees

CFetchEmployees

DListEmployees

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different procedure name than defined.

Omitting the parentheses after the procedure name.

To execute the stored procedure, use the exact procedure name GetAllEmployees with CALL.

3fill in blank

hard

Fix the error in the stored procedure that tries to update salary but misses the WHERE clause.

MySQL

CREATE PROCEDURE UpdateSalary(IN emp_id INT, IN new_salary DECIMAL(10,2)) BEGIN UPDATE employees SET salary = [1]; END;

Drag options to blanks, or click blank then click option'

Anew_salary

Bnew_salary WHERE id = emp_id

Csalary = new_salary WHERE id = emp_id

Dsalary WHERE id = emp_id = new_salary

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the WHERE clause, which updates all employees.

Incorrect syntax in the SET clause.

The UPDATE statement must set salary to new_salary and include a WHERE clause to target the correct employee by emp_id.

4fill in blank

hard

Fill both blanks to create a stored procedure that inserts a new employee with name and age.

MySQL

CREATE PROCEDURE AddEmployee(IN emp_name VARCHAR(50), IN emp_age INT) BEGIN INSERT INTO employees ([1], [2]) VALUES (emp_name, emp_age); END;

Drag options to blanks, or click blank then click option'

Aname

Bage

Csalary

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Using columns unrelated to the input parameters like salary or department.

Swapping the order of columns and values.

The columns to insert into are name and age matching the input parameters.

5fill in blank

hard

Fill all three blanks to create a stored procedure that deletes an employee by id and returns the number of affected rows.

MySQL

CREATE PROCEDURE DeleteEmployee(IN emp_id INT) BEGIN DELETE FROM employees WHERE id = [1]; SELECT ROW_COUNT() AS [2]; END;

Drag options to blanks, or click blank then click option'

Aemp_id

Baffected_rows

Cdeleted_count

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong variable name in the WHERE clause.

Not aliasing the ROW_COUNT() result.

The DELETE statement uses emp_id to identify the row, and affected_rows is the alias for the count of deleted rows.

Practice

1. Why do stored procedures help centralize logic in a MySQL database?

easy

A. Because they speed up the network connection

B. Because they automatically create database backups

C. Because they replace the need for tables

D. Because they keep all related SQL code in one place for reuse and maintenance

Solution

1. Step 1: Understand the role of stored procedures

   Stored procedures contain SQL code that can be executed repeatedly without rewriting it.

2. Step 2: Recognize centralization benefits

   By placing logic inside stored procedures, all applications use the same code, making maintenance easier and consistent.

3. Final Answer:

   Because they keep all related SQL code in one place for reuse and maintenance -> Option D

4. Quick Check:

   Centralizing logic = reuse and maintenance [OK]

Hint: Stored procedures group SQL logic centrally for easy reuse [OK]

Common Mistakes:

• Thinking stored procedures create backups
• Confusing stored procedures with tables
• Assuming stored procedures affect network speed

2. Which of the following is the correct syntax to create a stored procedure named GetUser in MySQL?

easy

A. CREATE PROCEDURE GetUser BEGIN SELECT * FROM users END

B. CREATE PROCEDURE GetUser() BEGIN SELECT * FROM users; END;

C. CREATE FUNCTION GetUser() SELECT * FROM users;

D. CREATE PROCEDURE GetUser() { SELECT * FROM users; }

Solution

1. Step 1: Recall MySQL stored procedure syntax

   Stored procedures use CREATE PROCEDURE name() BEGIN ... END; with semicolons inside.

2. Step 2: Check each option

   CREATE PROCEDURE GetUser() BEGIN SELECT * FROM users; END; uses correct syntax with BEGIN and END and semicolons; others miss BEGIN/END or use wrong keywords or braces.

3. Final Answer:

   CREATE PROCEDURE GetUser() BEGIN SELECT * FROM users; END; -> Option B

4. Quick Check:

   Correct syntax includes BEGIN...END with semicolons [OK]

Hint: Stored procedures need BEGIN and END blocks with semicolons [OK]

Common Mistakes:

• Using CREATE FUNCTION instead of PROCEDURE
• Omitting BEGIN and END
• Using curly braces instead of BEGIN/END

3. Given the stored procedure:

CREATE PROCEDURE GetCount()
BEGIN
  SELECT COUNT(*) AS total FROM orders;
END;

What will be the output when calling CALL GetCount(); if the orders table has 5 rows?

medium

A. A result set with one row and column 'total' showing 5

B. An error because no parameters are passed

C. No output because SELECT inside procedure does not return data

D. A result set with 5 rows showing order details

Solution

1. Step 1: Understand what the procedure does

   The procedure runs SELECT COUNT(*) from orders, which returns one row with the count.

2. Step 2: Predict output of CALL

   Calling the procedure returns the SELECT result as a result set with one row and column named 'total' showing 5.

3. Final Answer:

   A result set with one row and column 'total' showing 5 -> Option A

4. Quick Check:

   COUNT(*) returns number of rows = 5 [OK]

Hint: CALL runs procedure and returns SELECT results as output [OK]

Common Mistakes:

• Thinking SELECT inside procedure does not return data
• Confusing COUNT(*) with row details
• Expecting error due to no parameters

4. Consider this stored procedure code:

CREATE PROCEDURE UpdateStock()
BEGIN
  UPDATE products SET stock = stock - 1 WHERE id = 10
END;

What is the error in this code?

medium

A. Using UPDATE inside a procedure is not allowed

B. Incorrect procedure name syntax

C. Missing semicolon after UPDATE statement

D. Missing parentheses after procedure name

Solution

1. Step 1: Check syntax inside BEGIN...END

   Each statement inside BEGIN...END must end with a semicolon in MySQL.

2. Step 2: Identify missing semicolon

   The UPDATE line lacks a semicolon at the end, causing a syntax error.

3. Final Answer:

   Missing semicolon after UPDATE statement -> Option C

4. Quick Check:

   Statements inside BEGIN...END need semicolons [OK]

Hint: Always end statements inside procedures with semicolons [OK]

Common Mistakes:

• Forgetting semicolon after SQL statements
• Thinking procedure name syntax is wrong
• Believing UPDATE is disallowed in procedures

5. A company wants to ensure all applications update customer balances the same way. Which benefit of stored procedures best supports this goal?

hard

A. Stored procedures centralize logic to ensure consistent data handling

B. Stored procedures improve network speed for updates

C. Stored procedures automatically create audit logs

D. Stored procedures allow direct table access without permissions

Solution

1. Step 1: Understand the goal

   The company wants consistent updates to customer balances across all applications.

2. Step 2: Identify stored procedure benefit

   Centralizing update logic in stored procedures ensures all apps use the same code, preventing inconsistencies.

3. Final Answer:

   Stored procedures centralize logic to ensure consistent data handling -> Option A

4. Quick Check:

   Centralized logic = consistent data updates [OK]

Hint: Centralize update logic to keep data consistent across apps [OK]

Common Mistakes:

• Assuming stored procedures speed up network
• Thinking they auto-create audit logs
• Believing stored procedures bypass permissions