Update free-courses-pl.md (#6423)

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Co-authored-by: NImVector <59611597+LuigiImVector@users.noreply.github.com>

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books/free-programming-books-pl.md

@@ -188,6 +188,7 @@
 
 ### SQL
 
+* [Kurs SQL](https://dbadmin.net.pl/category/sql/) - Łukasz Bartnicki, (HTML) (:construction: *in process*)
 * [Kurs SQL](https://www.sqlpedia.pl/kurs-sql) - Jakub Kasprzak
 * [PL/SQL - podstawy (na stronie)](http://andrzejklusiewicz.blogspot.com/2010/11/kurs-oracle-plsql.html)
 * [SQL - podstawy (na stronie)](http://andrzejklusiewicz.blogspot.com/2010/11/kurs-oracle-sql.html)