ABS and MOD in MySQL

Introduction

ABS gives the positive value of a number, and MOD finds the remainder after division. They help with simple math tasks in databases.

When you want to ignore negative signs and get only positive numbers.

When you need to find out what remains after dividing one number by another.

When calculating distances or differences where only positive values make sense.

When checking if a number is even or odd using the remainder.

When splitting items into groups and seeing how many are left over.

Syntax

MySQL

ABS(number)
MOD(number, divisor)

ABS takes one number and returns its positive value.

MOD takes two numbers: the number and the divisor, and returns the remainder.

Examples

Returns 10 because ABS removes the negative sign.

MySQL

SELECT ABS(-10);

Returns 1 because 10 divided by 3 leaves a remainder of 1.

MySQL

SELECT MOD(10, 3);

Returns 5 because the number is already positive.

MySQL

SELECT ABS(5);

Returns 4 because 14 divided by 5 leaves a remainder of 4.

MySQL

SELECT MOD(14, 5);

Sample Program

This query shows how ABS converts -25 to 25 and MOD finds the remainder when 25 is divided by 4.

MySQL

SELECT ABS(-25) AS positive_value, MOD(25, 4) AS remainder;

Important Notes

ABS always returns a positive number or zero.

MOD returns zero if the first number is exactly divisible by the second.

If you use MOD with zero as divisor, it will cause an error.

Summary

ABS returns the positive value of any number.

MOD returns the remainder after division.

Both are useful for simple math operations in SQL queries.

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