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SQL Interview Preparation

Answer: Aggregate Records Using SUM

Explore how to apply the SQL SUM aggregate function to calculate total values from filtered data using aliases and conditional logic. Understand the role of SELECT queries, WHERE clauses, and CASE statements for flexible summations in SQL. Gain practical skills to solve similar interview questions involving aggregate functions.

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Solution

The solution is given below:

MySQL
/* The query to find the sum of students' marks in Mathematics */
SELECT SUM(Marks) AS TotalMarksMaths
FROM   StudentGrades
WHERE  Subject = 'Mathematics';

Explanation

The explanation of the solution code is given below:

  • Line 2: The SELECT query finds the sum of students’ marks for Mathematics. 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 specify the subject to filter the data. ...

Recall of relevant concepts