In Oracle Database, the UNION operator allows us to combine the results from two queries into a single result set.
Oracle
3 Ways to Create a Table if it Doesn’t Already Exist in Oracle
The very useful CREATE TABLE IF NOT EXISTS syntax was finally introduced in Oracle Database – Oracle Database 23c to be precise. This syntax allows us to run a CREATE TABLE statement without getting an error if the table already exists.
Earlier versions of Oracle don’t support the IF NOT EXISTS clause, and so if we want to avoid any nasty errors resulting from trying to create a table that already exists, we need to do a bit of extra work.
2 Ways to Return Rows that Contain Only Alphanumeric Characters in Oracle
Below are two methods for returning rows that only contain alphanumeric characters in Oracle Database.
Alphanumeric characters are alphabetic characters and numeric characters.
How to Format the Month in Roman Numerals in Oracle
Oracle Database provides us with the ability to return the month from a date using roman numerals.
For example, if the month is August, its decimal value would be 08 and it’s roman numeral equivalent would be VIII.
The way to do this is to use the RM or rm format element in your format mask. That will format the month using roman numerals in uppercase or lowercase respectively.
Specifying the date format can be done in several places.
How to Get Multiple Rows into a Comma Separated List in SQL
Most of the major RDBMSs have a function that enables us to return our query results as a comma separated list.
That is, we can use such a function to convert each row into a separate list item, within a comma separated list.
Below are examples of how to achieve this in some of the more popular RDBMSs.