computed columns

How to Create a Generated Column in MariaDB

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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.

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How to Create a Generated Column in Oracle

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Oracle 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.

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How to Create a Generated Column in PostgreSQL

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In PostgreSQL, a generated column is a special column that is always computed from other columns. A generated column doesn’t have a fixed value like in a base column. Rather, its value is determined by an expression that references other columns in the table.

Generated columns are included in the SQL standard (ISO/IEC 9075), and are supported by most major RDBMSs. Generated columns were first introduced in PostgreSQL 12.

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2 Ways to Get the Definition of a Generated Column in MySQL

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A generated column is one whose value is derived from an expression, as opposed to a fixed value. The expression typically uses other columns in the same table to compute the derived value.

We can create a generated column in MySQL very easily. But what if we want to go back later and see its definition?

Here are two options for returning the definition of a generated column in MySQL.

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Create a Generated Column in MySQL

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This article contains an example of adding a generated column to a table in MySQL.

Also known as computed columns, generated columns usually contain values that are dependent on other factors (such as the values in other columns).

Creating (or adding) a generated column in MySQL is basically the same as creating a normal column, except that the definition of the generated column contains an expression that determines the column’s value.

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Add a Generated Column to a Table in SQLite

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You can add a generated column to an existing table in SQLite by using the ALTER TABLE statement.

SQLite’s implementation of the ALTER TABLE statement is very limited, but it does allow you to add a column – including generated columns.

Generated columns (also known as “computed columns”) are columns that get their value from an expression that computes values from other columns.

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