Here are examples of using SQL to return rows that contain non-alphanumeric characters in various DBMSs.
Non-alphanumeric characters include punctuation characters like !@#&()–[{}]:;',?/* and symbols like `~$^+=<>“, as well as whitespace characters like the space or tab characters.
If you ever need to use SQL to return just the numeric values in a character column, the method you use will largely depend on your DBMS. Most DBMSs support regular expressions (regex), but some don’t. And some include functions that can detect numeric values.
Here are examples of how to do it in the more popular DBMSs.
Continue readingOracle Database supports the creation of generated columns. A generated column is a column whose value is derived from an expression that computes values from other columns.
In Oracle Database, generated columns are usually referred to as virtual columns. Generated columns can also be referred to as computed columns in other RDBMSs (such as SQL Server). Either way, they do pretty much the same thing – they contain an expression that computes a value based on values in other columns in the same table.
Continue readingMost RDBMSs provide at least a few ways to return rows that contain uppercase characters. Here are some options available in the major RDBMSs.
Continue readingHere’s an example of returning the first day of a given month in Oracle Database. We can return the first day of the current month, a previous or later month, or the first day of a month based on a specified date.
Continue readingBelow 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 readingSome 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).
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.
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 readingMost RDBMSs provide at least a few ways to return rows that contain lowercase characters. Here are some options available in the major RDBMSs.
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