Why ABS and MOD in MySQL? - Purpose & Use Cases

The Big Idea

Discover how simple functions can save you hours of tedious number crunching!

The Scenario

Imagine you have a list of numbers, some positive and some negative, and you need to find their absolute values or the remainder when divided by another number. Doing this by hand or with complex manual calculations can be confusing and slow.

The Problem

Manually calculating absolute values means checking each number's sign and changing negatives to positives, which is error-prone and tedious. Calculating remainders by hand for many numbers wastes time and can lead to mistakes, especially with large datasets.

The Solution

The ABS and MOD functions in SQL quickly and accurately handle these tasks. ABS returns the positive value of any number, and MOD gives the remainder after division, all with simple commands that work on entire columns of data at once.

Before vs After

✗ Before

if number < 0 then number = -number; remainder = number - FLOOR(number / divisor) * divisor;

✓ After

SELECT ABS(number), MOD(number, divisor) FROM table;

What It Enables

With ABS and MOD, you can instantly process and analyze numeric data for absolute values and remainders, enabling faster and more reliable data insights.

Real Life Example

For example, a store owner can use ABS to find the absolute difference between expected and actual sales, and MOD to determine if sales numbers fall into specific repeating patterns or cycles.

Key Takeaways

ABS and MOD simplify numeric calculations in databases.

They reduce errors and save time compared to manual methods.

These functions help analyze data patterns and values efficiently.

Practice

1. What does the ABS function do in MySQL?

easy

A. Returns the positive value of a number

B. Returns the remainder of a division

C. Returns the square root of a number

D. Returns the largest number in a column

Solution

1. Step 1: Understand the purpose of ABS

   The ABS function converts any number to its positive equivalent, removing any negative sign.

2. Step 2: Compare with other options

   MOD returns remainder, SQRT returns square root, and MAX returns largest value, so they are incorrect.

3. Final Answer:

   Returns the positive value of a number -> Option A

4. Quick Check:

   ABS(-5) = 5 [OK]

Hint: ABS always makes numbers positive, no matter the sign [OK]

Common Mistakes:

• Confusing ABS with MOD function
• Thinking ABS returns square root
• Assuming ABS finds max value

2. Which of the following is the correct syntax to get the remainder of 17 divided by 5 in MySQL?

easy

A. SELECT 17 / 5;

B. SELECT ABS(17, 5);

C. SELECT REMAINDER(17, 5);

D. SELECT MOD(17, 5);

Solution

1. Step 1: Identify correct function for remainder

   MOD is the MySQL function that returns the remainder after division.

2. Step 2: Check syntax correctness

   MOD takes two arguments: dividend and divisor. '/' operator performs division (17/5 = 3.4), ABS takes one argument, REMAINDER is not a MySQL function.

3. Final Answer:

   SELECT MOD(17, 5); -> Option D

4. Quick Check:

   MOD(17, 5) = 2 [OK]

Hint: Use MOD(a, b) to get remainder in MySQL [OK]

Common Mistakes:

• Using ABS instead of MOD for remainder
• Trying to use '/' operator for remainder
• Using non-existent REMAINDER function

3. What is the output of this query?

SELECT ABS(-12) AS abs_val, MOD(29, 6) AS mod_val;

medium

A. abs_val = 12, mod_val = 5

B. abs_val = -12, mod_val = 5

C. abs_val = 12, mod_val = 23

D. abs_val = -12, mod_val = 23

Solution

1. Step 1: Calculate ABS(-12)

   ABS returns the positive value, so ABS(-12) = 12.

2. Step 2: Calculate MOD(29, 6)

   29 divided by 6 is 4 remainder 5, so MOD(29, 6) = 5.

3. Final Answer:

   abs_val = 12, mod_val = 5 -> Option A

4. Quick Check:

   ABS(-12) = 12, MOD(29,6) = 5 [OK]

Hint: ABS removes sign; MOD gives remainder after division [OK]

Common Mistakes:

• Forgetting ABS makes negative positive
• Mixing up MOD result with division quotient
• Assuming MOD returns division result

4. Identify the error in this MySQL query:

SELECT ABS(-7, 3), MOD(10);

medium

A. Both functions are used correctly

B. ABS function has too many arguments; MOD function missing second argument

C. ABS function missing second argument; MOD function has too many arguments

D. MOD function should be ABS

Solution

1. Step 1: Check ABS function arguments

   ABS takes only one argument, but here it has two (-7, 3), which is incorrect.

2. Step 2: Check MOD function arguments

   MOD requires two arguments, but only one (10) is provided, so it's missing the second argument.

3. Final Answer:

   ABS function has too many arguments; MOD function missing second argument -> Option B

4. Quick Check:

   ABS(-7) valid; MOD(10, x) needs two args [OK]

Hint: ABS needs 1 arg; MOD needs 2 args [OK]

Common Mistakes:

• Passing multiple arguments to ABS
• Using MOD with only one argument
• Assuming MOD can be called like ABS

5. You want to select all rows from a table numbers where the absolute value of the column val divided by 4 leaves a remainder of 1. Which query correctly achieves this?

hard

A. SELECT * FROM numbers WHERE ABS(MOD(val, 4)) = 1;

B. SELECT * FROM numbers WHERE MOD(val, 4) = 1;

C. SELECT * FROM numbers WHERE MOD(ABS(val), 4) = 1;

D. SELECT * FROM numbers WHERE ABS(val) / 4 = 1;

Solution

1. Step 1: Understand the condition

   We want the remainder after dividing the absolute value of val by 4 to be 1.

2. Step 2: Analyze each option

   SELECT * FROM numbers WHERE MOD(val, 4) = 1; uses val directly, ignoring absolute value. SELECT * FROM numbers WHERE MOD(ABS(val), 4) = 1; correctly applies ABS(val) inside MOD. SELECT * FROM numbers WHERE ABS(MOD(val, 4)) = 1; applies ABS after MOD, which can give wrong results if val is negative. SELECT * FROM numbers WHERE ABS(val) / 4 = 1; uses '/' which performs division, not remainder.

3. Final Answer:

   SELECT * FROM numbers WHERE MOD(ABS(val), 4) = 1; -> Option C

4. Quick Check:

   MOD(ABS(val), 4) = 1 filters correctly [OK]

Hint: Apply ABS inside MOD to get remainder of positive value [OK]

Common Mistakes:

• Applying ABS after MOD instead of before
• Using '/' operator for remainder
• Ignoring absolute value in condition