Below are examples of using SQL to return the last day of the month across various DBMSs.
This could be the last day of the current month, or the last day of a month based on a given date.
Continue readingCategory: MariaDB
SQL NVL2() Explained
Some DBMSs have an NVL2() function that allows us to replace a value with another value, the new value being determined by whether or not the initial value is null.
It’s similar to the NVL() function, except that NVL2() accepts exactly three arguments. This allows us to specify a different value to return in the event the first argument is not null.
In contrast, with the NVL() function, some DBMSs accept only two arguments (which makes the function a synonym for the IFNULL() function) while others accept an unlimited number of arguments (which makes it a synonym for the COALESCE() function).
SQL NVL() Explained
Some DBMSs provide an NVL() function, which can be used when working with potentially NULL values. The function allows us to replace any NULL values with another value.
Find Duplicate Rows that have a Primary Key in SQL
Here are examples of using SQL to return duplicate rows when those rows have a primary key or other unique identifier column.
These queries work in most of the major RDBMSs, including SQL Server, Oracle, MySQL, MariaDB, PostgreSQL, and SQLite.
Continue readingFind Rows that Contain Lowercase Characters in SQL
Most RDBMSs provide at least a few ways to return rows that contain lowercase characters. Here are some options available in the major RDBMSs.
Continue readingSelect Duplicate Rows in SQL
Here’s an example of using SQL to find duplicate rows in a database table. This technique can be used in most of the major RDBMSs, including SQL Server, Oracle, MySQL, MariaDB, PostgreSQL, and SQLite.
Continue readingHow to Convert a Unix Timestamp to a Date/Time in SQL
Here are examples of converting a Unix timestamp to a date/time value in some of the major RDBMSs.
The Unix timestamp (also known as Unix Epoch time, Unix time, or POSIX time) is the number of seconds that have elapsed since 00:00:00 Thursday, 1 January 1970, Coordinated Universal Time (UTC).
Continue readingReturn Rows that Contain Only Alphanumeric Characters in SQL
Alphanumeric characters are alphabetic characters and numeric characters.
Below are examples of using SQL to return rows that contain only alphanumeric characters.
Continue readingSQL ISNULL() Explained
Some RDBMSs provide an ISNULL() function that can be used when dealing with potentially null values.
MySQL, MariaDB, and Oracle Database each have an ISNULL() function that returns 1 if its argument is null, and 0 if it’s not.
SQL Server also has an ISNULL() function, but it works differently. It works more like how the IFNULL() function works in some other RDBMSs.
Other RDBMSs, such as PostgreSQL and SQLite don’t include an ISNULL() function, but they do support the IS NULL predicate (as do the other RDBMSs).
MariaDB CASE Operator
In MariaDB, we can use the CASE operator to compare a list of conditions and return a different result depending on which condition (if any) is matched.
The CASE expression is included in the SQL standard (ISO/IEC 9075), and most major RDBMSs support it.
MariaDB also has the CASE statement, which is slightly different to the CASE operator. This article is about the CASE operator.