docs(mysql): mention mandatory primary keys for MySQL 8

src/_posts/databases/mysql/2000-01-01-overview.md

@@ -51,6 +51,18 @@ The latest version of MySQL® available is **`8.0.40-1`**.
 This is also the default version when attaching a MySQL® addon to your
 application.
 
+### Requirements
+
+For MySQL versions 8 and higher, every tables must have a primary key.
+
+If you need to add a primary key to the `foo` table. You need to
+evaluate the impact of this modification before proceeding. Here is an example
+SQL statement to add a new column and set it as primary:
+
+```sql
+ALTER TABLE 'foo' ADD COLUMN <column description> PRIMARY KEY;
+```
+
 ### Billing
 
 Billing of your MySQL® addon is done on a minute basis.