Database Management Systems
In SQLite, the json_extract() function extracts and returns one or more values from well-formed JSON.
We pass the JSON as an argument when we call the function, and it returns the applicable value/s.
We can specify one or more paths to extract from the JSON document.
When using the UNION operator in MariaDB, you may encounter the following error: “ERROR 1222 (21000): The used SELECT statements have a different number of columns”.
This error occurs when the number of columns returned by each SELECT statement is different.
The way to fix this is to ensure that both SELECT statements return the same number of columns.
In PostgreSQL, we can use the + operator to add one or more years to a date.
In SQLite, the json_array_length() function returns the number of elements in a given JSON array.
The array is provided as an argument. If the array is embedded within a larger JSON document, we can use an optional second argument to specify the path to the array.
If the value is not an array, the function returns 0.
The following MySQL query returns only those rows that have numeric values in a given column.
The SQLite json_group_object() function is an aggregate function that returns a JSON object comprised of all name/value pairs in the aggregation.
In other words, it constructs a JSON object from the values provided by its arguments.
The SQLite json_group_array() function is an aggregate function that returns a JSON array comprised of all values in the aggregation.
In other words, it constructs an array from the values provided by its argument.
In SQLite, the json_valid() function checks whether or not its argument is well-formed JSON.
It returns 1 if the argument is well-formed JSON, and 0 if it’s not.
In SQLite, the json_array() function returns a well-formed JSON array based on its arguments.
The function accepts zero or more arguments, and each argument becomes an element in the resulting array.
The SQLite json_object() function returns a well-formed JSON object based on its arguments.
The function accepts zero or more pairs of arguments and returns a well-formed JSON object based on those arguments.