MySQL includes an aggregate function called JSON_OBJECTAGG(). This function enables you to create a JSON object containing key-value pairs. More specifically, it lets you create this JSON object based on the results of a query.
It accepts two arguments, the first of these being used as a key and the second as a value. These arguments can be column names or expressions.
Among the many MySQL aggregate functions is one called JSON_ARRAYAGG(). This function enables you to aggregate a result set as a single JSON array. Each row of the result set ends up as a single element in the array.
The order of the elements in the array is undefined.
In MySQL, the difference between the MIN() and LEAST() functions is exactly the same as the difference between the MAX() and GREATEST() functions.
In each case, both functions perform a similar operation, but they do have a different syntax.
At first glance, the MySQL MAX() and GREATEST() functions perform a similar operation. They both return the maximum value from a range of values. However, there’s a difference between these two functions.
The best way to see the difference between these two functions is to compare their syntax.
The MySQL LEAST() function is a comparison function that returns the smallest value from a list of values.
The list of values is provided as multiple arguments. So in other words, LEAST() returns the minimum-valued argument from a list of arguments.
The MySQL GREATEST() function is a comparison function that returns the largest value from a list of values.
The list of values is provided as multiple arguments. So in other words, GREATEST() returns the maximum-valued argument from a list of arguments.
The MySQL MIN() function is an aggregate function that returns the minimum value from an expression.
Typically, the expression would be a range of values returned as separate rows in a column, and you can use this function to find the minimum value from the returned rows. If there are no matching rows, MIN() returns NULL.
For example, you can use this function to find out which city has the smallest population out of a list of cities.
The MySQL MAX() function is an aggregate function that returns the maximum value from an expression.
Typically, the expression would be a range of values returned as separate rows in a column, and you can use this function to find the maximum value from the returned rows. If there are no matching rows, MAX() returns NULL.
For example, you can use this function to find out which city has the largest population out of a list of cities.
In MySQL, the ORD() function returns the numeric value of the leftmost character of a given string. You provide the string as an argument.
If the leftmost character is a multibyte character, the returned value is calculated from the numeric values of its constituent bytes. If the leftmost character is not a multibyte character, the return value is its ASCII code (which is the same result as when using the ASCII() function).
In MySQL, the ASCII() function returns the numeric ASCII code of the leftmost character of a given string. You provide the string as an argument.
This article contains examples of usage.