## Table of content

- Introduction
- Basic Concepts
- Method 1: Modulus Operator
- Method 2: Bitwise AND Operator
- Method 3: CASE Statement
- Bonus Method: Regular Expressions
- Conclusion

### Introduction

When working with SQL code, it's important to be able to distinguish between even and odd numbers, as this can be useful in a variety of situations. In this article, we'll explore some code examples that can help you master the art of distinguishing even and odd numbers in SQL.

To begin with, it's important to understand the basics of even and odd numbers. Even numbers are those that can be divided evenly by 2, with no remainder. Odd numbers, on the other hand, cannot be divided evenly by 2 and will always have a remainder of 1.

With this in mind, we can start to look at some code examples that can help us distinguish between even and odd numbers in SQL. One common way to do this is to use the modulus operator (%), which returns the remainder of a division operation.

For example, suppose we have a table of numbers and we want to select only the even numbers. We can use the following code:

SELECT number FROM table_name WHERE number % 2 = 0;

This code uses the modulus operator to check if each number in the table is even (i.e., the remainder when dividing by 2 is 0). If the remainder is 0, the number is even and will be selected.

Similarly, if we want to select only the odd numbers from the same table, we can use the following code:

SELECT number FROM table_name WHERE number % 2 = 1;

This code checks if each number is odd (i.e., the remainder when dividing by 2 is 1), and selects only those that meet this criterion.

By using code like this, we can easily distinguish even and odd numbers in SQL and use this information in a variety of ways, from filtering data to performing calculations. With these examples as a starting point, you'll be well on your way to mastering the art of distinguishing even and odd numbers in SQL.

### Basic Concepts

In SQL, even and odd numbers can be easily distinguished using the modulus operator %. This operator returns the remainder of a division operation. When a number is divided by 2, the remainder will be 0 if the number is even, and 1 if the number is odd.

To use the modulus operator in SQL, simply write the number to be tested, followed by the % symbol, and then the divisor (in this case 2). For example, the expression "SELECT 5 % 2" will return 1, indicating that 5 is odd.

SQL also provides the if statement for conditional logic. The if statement allows you to execute different actions based on the outcome of a logical operation. The basic structure of an if statement in SQL is:

```
IF logical_expression
BEGIN
statement_1
statement_2
...
END
```

The logical_expression is the condition to be tested. If it is true, the statements within the BEGIN and END block will be executed. If it is false, the statements will be skipped.

To distinguish even and odd numbers in SQL using the if statement, you can combine the modulus operator with the if statement. For example, the following query will select even numbers from a table called numbers:

```
SELECT number FROM numbers
WHERE (number % 2) = 0;
```

The query checks if the remainder of each number divided by 2 is equal to 0. If so, the number is even and will be returned in the query results.

Overall, understanding these will help you to distinguish even and odd numbers in SQL using code expressions like modulus operator and if statements. The following sections will provide more advanced code examples to further improve your knowledge on this topic.

### Method 1: Modulus Operator

The modulus operator (%) is a simple yet powerful tool for determining whether an integer is odd or even. In Python, the modulus operator returns the remainder when dividing two integers. For instance, 5 % 2 returns 1 because the remainder when dividing 5 by 2 is 1. Similarly, 6 % 2 returns 0 because there is no remainder when dividing 6 by 2.

Using the modulus operator, we can easily determine whether an integer is odd or even. The convention is that even numbers have a remainder of 0 when divided by 2, while odd numbers have a remainder of 1. To test if a number is even, we check if the modulus of the number divided by 2 is 0. For example, the following code checks if the number 6 is even:

```
if 6 % 2 == 0:
print("6 is even")
else:
print("6 is odd")
```

This code will output "6 is even" because the modulus of 6 divided by 2 is 0. Similarly, we can check if a number is odd by checking if the modulus of the number divided by 2 is 1. For example, the following code checks if the number 5 is odd:

```
if 5 % 2 == 1:
print("5 is odd")
else:
print("5 is even")
```

This code will output "5 is odd" because the modulus of 5 divided by 2 is 1.

### Method 2: Bitwise AND Operator

In Python, the bitwise AND operator is represented by the "&" symbol. To use this operator to determine whether a number is even or odd, you need to know that all even numbers have a 0 in their least significant bit, while odd numbers have a 1.

To apply the bitwise AND operator to a number, you first convert it to binary. You can do this using the built-in bin() function, which takes an integer as input and returns a string representing its binary value.

Once you have the binary representation of the number, you can use the bitwise AND operator to check its least significant bit. To do this, you bitwise AND the number with 1 (which has a binary representation of 00000001). If the result is 0, the number is even, while if it is 1, the number is odd.

Here's an example:

```
num = 7
bin_num = bin(num)
lsb = int(bin_num[-1]) # convert the last character of the binary string to an integer
if lsb & 1:
print(num, "is odd")
else:
print(num, "is even")
```

In this example, we first set `num`

to 7. We then use the `bin()`

function to get its binary representation, which is the string "0b111". We convert the last character of this string to an integer using the `int()`

function, giving us 1 (which is the least significant bit of 7). We then use the bitwise AND operator to check whether this bit is 1. Since it is, we print "7 is odd".

### Method 3: CASE Statement

In addition to the IF and ELSE statements, you can also use the CASE statement in SQL to determine if a number is even or odd. The CASE statement allows you to set multiple conditions and specify different actions for those conditions, similar to a switch statement in other programming languages.

Here is an example of how to use the CASE statement to determine if a number is even or odd:

```
SELECT number,
CASE
WHEN number % 2 = 0 THEN 'Even'
ELSE 'Odd'
END AS 'Even/Odd'
FROM numbers_table;
```

In this example, we are selecting the column "number" from the table "numbers_table". We then use the CASE statement to check if the number is even or odd. The condition "number % 2 = 0" checks if the number is divisible by 2 without a remainder, indicating that it is even. If the condition is true, the result will display "Even". If the condition is false, the result will display "Odd".

We use the AS keyword to give the resulting column a new name of "Even/Odd".

It is important to note that the CASE statement can be used with multiple conditions, each with its own action. This makes it a versatile tool for many different situations in SQL programming.

### Bonus Method: Regular Expressions

Regular expressions, also known as regex, are a powerful tool for manipulating text in Python programming. They can be used to search for and match patterns within strings or text. In the context of distinguishing even and odd numbers, regular expressions can help us quickly identify patterns that match either even or odd numbers.

Here's an example of how we can use regular expressions to distinguish even and odd numbers. First, we define a regular expression pattern that matches even numbers:

```
import re
pattern = r'\b[02468]+\b'
re_obj = re.compile(pattern)
```

In this code, we're using the `re`

module to create a regular expression object (`re_obj`

) based on the `pattern`

we defined. The pattern matches one or more characters (`+`

) that are either 0, 2, 4, 6, or 8, surrounded by word boundaries (`\b`

). This will match any string that contains only even digits.

We can then use the `search`

method of the regular expression object to find matches within a given string:

```
string = 'Here are some numbers: 123 456 789 2468 13579'
matches = re_obj.search(string)
```

This code will search for the regular expression pattern within the `string`

variable, and return the first match it finds (`2468`

).

We can do the same thing for odd numbers by defining a different regular expression pattern that matches only odd digits:

```
pattern = r'\b[13579]+\b'
re_obj = re.compile(pattern)
string = 'Here are some numbers: 123 456 789 2468 13579'
matches = re_obj.search(string)
```

This time, the regular expression pattern matches one or more characters that are either 1, 3, 5, 7, or 9. When we run this code, the `search`

method will return the first odd number it finds (`13579`

).

Using regular expressions can be a powerful way to quickly identify even and odd numbers within text. By defining patterns that match specific sets of digits, we can easily filter out irrelevant numbers and focus only on those that are even or odd.

### Conclusion

In , being able to distinguish between even and odd numbers is a basic building block of programming, and understanding this concept is crucial for any programmer working with numerical data. Through this article, we have explored several code examples that allow you to identify even and odd numbers in SQL.

From the simple "WHERE" clause to the more complex "CASE" statement, there are many techniques that you can use to filter data based on whether it is even or odd. Additionally, we also looked at how to use built-in SQL functions such as MOD and ABS to achieve the same outcome.

By mastering these techniques, you will be able to write cleaner and more efficient code, leading to better results and faster analysis. While there is much more to learn in SQL programming, having a solid understanding of how to distinguish between even and odd numbers is a great starting point.

We hope this article has been informative, and that it has given you the tools you need to start working with even and odd numbers in your SQL queries. Remember, practice makes perfect, so keep experimenting with different code examples and building your skills to become a SQL master!