Search⌘ K
AI Features
Home
Courses
SQL Interview Preparation

Answer: Aggregate Records Using COUNT

Explore how to apply the COUNT aggregate function in SQL to count records based on specific conditions, including handling NULL values. Understand different query approaches, such as using CASE, SUM, and negated COUNT, to solve common interview questions and strengthen your SQL skills.

We'll cover the following...

Solution

The solution is given below:

MySQL
/* The query to find the count of exams missed */
SELECT COUNT(*) AS AbsentStudents
FROM   StudentGrades
WHERE  Marks IS NULL;

Explanation

The explanation of the solution code is given below:

  • Line 2: The SELECT query uses the COUNT(*) function to count the number of rows in the table. We use AS to set an alias for the column.

  • Line 3: The FROM clause specifies the table, StudentGrades.

  • Line 4: In the WHERE clause, we specified the condition to filter the data. The IS NULL keyword is used specifically to check if the value is NULL.

Recall of relevant concepts

We have covered the ...