Database Management Systems
When using JSON documents with MySQL, we can use the JSON_ARRAY_APPEND() function to append new values to an array.
The way it works is, you provide the JSON document as the first argument, then follow that up with the path to append to, followed by the value to append.
In MySQL 5.7, this function was called JSON_APPEND() but that name is no longer supported.
When working with JSON and MySQL, sometimes you might need to escape strings so that their quote characters don’t interfere with the interpretation of the JSON document. In such cases, you can use the JSON_QUOTE() function to escape potentially problematic strings.
JSON_QUOTE() is used to produce a valid JSON string literal that can be included in a JSON document. For example, you might want an element in an array to have the text null as a string literal, rather than having an actual null value. This function can be used to ensure that the text is added as a string literal, rather than a null value.
To use it, simply call the function while passing in the string.
In MySQL, you can use the JSON_OBJECT() function to create a JSON object from a list of key/value pairs. You provide each key/value pair as two separate arguments. Each pair becomes a key/value pair in the resulting JSON object.
You must provide an even number of arguments (otherwise, you’d have an incomplete pair somewhere in your list of arguments).
The function also accepts an empty list (i.e. you provide no arguments). In this case, you’ll get an empty object.
In MySQL, you can use the JSON_ARRAY() function to create a JSON array from a list of values. You provide each value as a separate argument. Each argument becomes a separate element of the array.
The function also accepts an empty list (i.e. you provide no arguments). In this case, you’ll get an empty array.
MySQLÂ 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 MySQLÂ 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.