Virtual and persistent columns
We described a view on a virtual table, meaning that its contents are the results of a query. The idea behind virtual columns is very similar: they are columns based on SQL expressions.
A virtual column overview
The terminology is a bit confusing here. In fact, all automatically calculated columns are called virtual columns in MariaDB KnowledgeBase. However, there are two types of virtual columns: VIRTUAL columns and PERSISTENT columns.
- A
VIRTUALcolumn is calculated on-the-fly when it is referenced in a statement—for example, when aSELECTclause extracts its value. This is the default type. - A
PERSISTENTcolumn is written in the table and its value can be read when needed, as happens with regular columns.
Calculating ...
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