Here are five ways to see whether a table contains a generated column in MariaDB.
Relational
5 Ways to See if a Table has a Generated Column in MySQL
MySQL supports generated columns. If you’re not sure whether a table has a generated column or not, you can check it using any of the following methods.
Subtract Months from a Date in SQLite
In SQLite, we can use the DATE() function to subtract one or more months from a date.
For datetime values, we can use the DATETIME() function.
Get the First, Second, Third, or Fourth Monday of a Year in SQLite
We can use SQLite’s DATE() function to return the first, second, third, fourth, etc instance of a given day within a given year.
We can use the same technique to return the first Monday of each month in the year.
It’s not limited to Monday though. The same techniques can be used on Tuesday, Wednesday, Thursday, Friday, etc.
How to Create a Generated Column in MariaDB
A generated column is a database column whose value is an expression. Therefore, the value of the generated column is usually derived (for example, it could be derived from values in other columns).
Generated columns are also sometimes referred to as computed columns or virtual columns.
Creating a generated column in MariaDB is essentially the same as creating a normal column. The difference is that the definition of the generated column contains an expression that determines the column’s value.
Subtract Seconds from a Time Value in SQLite
In SQLite, we can use the TIME() function to subtract one or more seconds from a time value.
For datetime values, we can use the DATETIME() function.
How to Delete Duplicate Rows that have a Primary Key in SQL
The following examples use SQL to delete duplicate rows that have a primary key or unique identifier column.
Specifically, the examples delete all duplicates except one. So for example, in the case of three identical rows, it deletes two of them and keeps one.