MySQL Operations and Built-in Functions – String, Number, Date, and
Advanced Functions
MySQL is a popular open-source relational database management system that is widely used for developing web applications. It is often called the world’s most popular open-source database.
MySQL has a rich set of built-in functions that you can use to perform various operations on your data. These functions are designed to help you manipulate strings, numbers, dates, and other types of data in your database.
In this article, we will explore some of the most commonly used MySQL operations and built-in functions.
String Functions
A string is simply a series of characters that are enclosed in quotes. MySQL provides a wide range of functions for manipulating strings.
The CONCAT function is used to concatenate two or more strings together. For instance, the code SELECT CONCAT(“Hello”, “World”); will output the string “HelloWorld”.
The REVERSE function returns the string in reverse order. The POSITION function returns the position of a substring within a string.
For instance, the code SELECT POSITION(“is”, “This is a test”); will output the integer 3, since the substring “is” is found at the third position of the string “This is a test”. Other useful string functions include:
– LENGTH: returns the length of a string
– SUBSTRING: extracts a substring from a string
– TRIM: removes leading and trailing spaces from a string
– REPLACE: replaces a substring with another substring
– UPPER/LOWER: converts a string to uppercase or lowercase
Number Functions
MySQL provides several built-in functions for manipulating numbers. The MIN function returns the minimum value in a set of values.
For instance, the code SELECT MIN(5, 2, 9); will output the integer 2. The MAX function returns the maximum value in a set of values.
For instance, the code SELECT MAX(5, 2, 9); will output the integer 9. The TRUNCATE function is used to truncate a number to a given number of decimal places.
Other useful number functions include:
– ABS: returns the absolute value of a number
– CEILING/FLOOR: rounds a number up or down to the nearest integer
– ROUND: rounds a number to a given number of decimal places
– POW: raises a number to a power
Date Functions
MySQL also provides a rich set of functions for working with dates and times. The DATE function is used to extract the date part of a timestamp.
For instance, the code SELECT DATE(‘2022-12-31 23:59:59’); will output the date ‘2022-12-31’. The DAYOFMONTH function returns the day of the month for a given date.
For instance, the code SELECT DAYOFMONTH(‘2022-12-31’); will output the integer 31, since it is the 31st day of December. The DATE_ADD function adds a time interval to a given date, while the DATE_SUB function subtracts a time interval from a given date.
Other useful date functions include:
– DAYNAME: returns the name of the day for a given date
– WEEKDAY: returns the index of the day of the week for a given date
– MONTH: returns the month for a given date
– YEAR: returns the year for a given date
Advanced Functions
MySQL also provides advanced functions that are useful for more complex operations. The IF function is used to perform a conditional operation.
It takes three arguments: a test expression, a result for a true condition, and a result for a false condition. The code SELECT IF(10 > 5, ‘Yes’, ‘No’); will output the string “Yes”, since the test expression “10 > 5” is true.
The COALESCE function is used to return the first non-null value in a list of values. Another useful advanced function is the GROUP_CONCAT function, which is used to concatenate the values of a group of rows into a single string.
In conclusion, MySQL’s built-in functions are a powerful tool for developers to manipulate data within a database. MySQL provides functions for manipulating strings, numbers, dates, and a range of more advanced functions.
Understanding how to use MySQL built-in functions can help you write more complex and efficient SQL queries. Practicing with the functions discussed in this article will help you become more proficient in MySQL database development, saving you time and effort in the long run.
Subtracting Dates in MySQL – Querying Date of Birth (DOB) Within a Range
MySQL provides a simple and effective way for querying a range of dates using the WHERE keyword as a conditional operator. In this article, we will explore how to subtract dates in MySQL, using the DATE_SUB function, to retrieve date of birth (DOB) values within a given age range.
The first step in creating a MySQL statement to retrieve DOB values within an age range is to use the DATE_SUB function. This function is used to perform subtraction operations on a given date.
Using the DATE_SUB Function to Subtract Dates
The DATE_SUB function is used to subtract a time interval from a given date. The function takes two arguments, the date to be subtracted from and the time interval to subtract.
The time interval argument can be expressed in various forms such as minute, hour, day, week, month, quarter, and year. For example, to subtract one year from a given date, you can use the following syntax:
SELECT DATE_SUB(‘2022-10-01’, INTERVAL 1 YEAR);
This will return the date ‘2021-10-01’.
Querying DOB Values Within a Range
To query a range of DOB values, we can use the BETWEEN operator to select values within an inclusive date range. The BETWEEN operator works with the WHERE keyword as a conditional operator to select rows within a given range.
For example, to select all DOB values between January 1st, 1980 and December 31st, 2000, we can use the following SQL statement:
SELECT DOB FROM Persons WHERE DOB BETWEEN ‘1980-01-01’ AND ‘2000-12-31’;
In this example, ‘Persons’ is the name of the table, DOB is the name of the column containing the date of birth values, and ‘1980-01-01’ and ‘2000-12-31’ represent the inclusive date range.
Using the NOW Function to Obtain Current Date and Time
Another useful function in MySQL is the NOW function. This function returns the current date and time in the format ‘YYYY-MM-DD HH:MM:SS’.
It is commonly used to keep track of the time that a record was created or updated. Here is an example of how to use the NOW function:
INSERT INTO Persons (Name, DOB, Created_DateTime)
VALUES (‘John’, ‘1990-05-15’, NOW());
In this example, ‘Persons’ is the table name, ‘Name’ and ‘DOB’ are the column names, and ‘John’ and ‘1990-05-15’ represent the sample data.
The ‘Created_DateTime’ column will store the current date and time when this record is inserted.
Arguments in the Date_Sub Function
The DATE_SUB function can be used with various arguments to subtract specific intervals of time from a given date. The syntax for the function is as follows:
DATE_SUB(date, INTERVAL value type)
The date argument represents the date from which the interval will be subtracted, and the value argument represents the quantity of the interval type that should be subtracted.
The type argument represents the type of interval that will be subtracted (minute, hour, day, week, month, quarter, or year). For instance, to subtract 6 months from a given date, you can use the following SQL statement:
SELECT DATE_SUB(‘2022-10-01’, INTERVAL 6 MONTH);
This will return the date ‘2022-04-01’.
In conclusion, MySQL provides a simple and effective way for querying DOB values within an age range by using the DATE_SUB function to subtract intervals of time from a given date. The BETWEEN operator can be used with the WHERE keyword to select values within an inclusive date range.
The NOW function is useful for obtaining the current date and time, and the DATE_SUB function provides a way to subtract intervals of time from a given date using various arguments. These features of MySQL make it an excellent choice for database management and querying.
In conclusion, this article covered several important topics related to working with dates in MySQL. We explored how to subtract dates using the DATE_SUB function, how to query DOB values within an age range using the BETWEEN operator, and how to use the NOW function to obtain the current date and time.
Understanding these concepts is crucial for developers working with MySQL databases, as it allows them to query, update, and manipulate data effectively. By practicing these techniques, developers can become more proficient in MySQL database development and save time and effort in the long run.
As technology evolves, it is important to stay up-to-date with new features and tools that can lead to more efficient and effective data management.