In MariaDB, the EXCEPT operator returns rows from the left input query that aren’t output by the right input query.
Another way of putting it is that it returns all rows from the left SELECT result set except rows that are in right SELECT result set.
When working with JSON in MariaDB, you can use JSONPath expressions to manipulate data within a JSON document.
One powerful feature that MariaDB provides is the wildcard step (**). This allows you to recursively select all child elements of the current element.
The wildcard step is a non-standard extension, and it’s also supported with the same meaning in MySQL.
In SQL Server, the NULLIF() expression checks the value of two specified expressions. It returns a null value if they’re equal, otherwise it returns the first expression.
In MySQL, the SCHEMA() function is a synonym for the DATABASE() function. It returns the default (current) database name.
The result is returned as a string in the utf8 character set. If there is no default database, it returns NULL.
In PostgreSQL, the SUM() function computes the sum of the non-null input values and returns the result.
In other words, it adds numbers and returns the result.
In PostgreSQL, the AVG() function computes the average (arithmetic mean) of all the non-null input values, and returns the result.
Some DBMSs such as Oracle, MySQL, and MariaDB have a DESCRIBE command that returns information about tables and views. It goes DESCRIBE table where table is the name of the table or view, and it can also be followed by a column name if you only want information about a specific column.
PostgreSQL doesn’t have a DESCRIBE TABLE command as such, but there are alternatives.
In SQL Server, the SUM() aggregate function returns the sum of a given expression.
It can also be used to return the sum of all distinct (unique) values in the expression.
SUM() only works on numeric columns. Null values are ignored.
In SQL Server, the TRY_CONVERT() function is very similar to the CONVERT() function, except that TRY_CONVERT() doesn’t return an error if the conversion fails (CONVERT() does).
Instead, the TRY_CONVERT() function returns NULL if the conversion doesn’t succeed.
There are some occasions however, where TRY_CONVERT() will return an error.
In SQL Server, the CONVERT() function converts an expression of one data type to another.
Here’s a quick overview of the function with examples.