..  _important-1785882500:

=======================================================
Important: The `link` column of `pages` is nullable now
=======================================================

Description
===========

The extension adds a :sql:`link` column to the shared :sql:`pages` table.
It was declared as:

..  code-block:: sql

    link text NOT NULL DEFAULT '',

MySQL cannot store a plain default value on a :sql:`TEXT` column. TYPO3 v13
works around that by writing the default in the :sql:`DEFAULT ('')` syntax
MySQL 8.0.13 introduced. TYPO3 v12 does not, so there the column was created
:sql:`NOT NULL` with no default at all. Every statement that does not name the
column was then rejected, and that includes creating a page in the backend:

..  code-block:: text

    SQL error: "Field 'link' doesn't have a default value" (pages:NEW1)

No page was created. MariaDB, PostgreSQL and SQLite were never affected.

The column keeps its type and loses the default instead:

..  code-block:: sql

    link text DEFAULT NULL,

Impact
======

Creating a page works again on TYPO3 v12 with MySQL.

Records written without naming the column now store :sql:`NULL` where
they previously stored an empty string. Existing rows are not changed, so
the column can hold both. Code that reads it should compare with
:php:`empty()` rather than with :php:`''`.

Affected Installations
======================

All installations of this extension. The database schema has to be
updated, either in :guilabel:`Admin Tools > Maintenance > Analyze Database
Structure` or with :bash:`vendor/bin/typo3 extension:setup`. The change only
relaxes the column, so no data is converted and nothing can be lost.

..  index:: Database, ext:academic_partners