added DatabaseSystems in free-course-hi.nd and two courses in it (#7318)

* added DatabaseSystems in free-course-hi.nd and two courses in it

* changed Database Systems to Databases

* Update free-courses-hi.md

* Update courses/free-courses-hi.md

Co-authored-by: Eric Hellman <eric@hellman.net>

* Update courses/free-courses-hi.md

Co-authored-by: Eric Hellman <eric@hellman.net>

Co-authored-by: Eric Hellman <eric@hellman.net>

courses/free-courses-hi.md

@@ -12,6 +12,7 @@
 * [Compiler Design](#compiler-design)
 * [Computer Organization and Architecture](#computer-organization-and-architecture)
 * [Data Structures](#data-structures)
+* [Databases](#databases)
 * [DevOps](#devops)
 * [Flutter](#flutter)
 * [Git and GitHub](#git-and-github)
@@ -145,6 +146,12 @@
 * [Stack Playlist \| Interview Questions \| Coding \| Tutorials \| Data Structures](https://www.youtube.com/playlist?list=PL_z_8CaSLPWdeOezg68SKkeLN4-T_jNHd) - Aditya Verma
 
 
+### Databases
+
+* [DBMS (Database Management System)Complete Playlist](https://www.youtube.com/playlist?list=PLxCzCOWd7aiFAN6I8CuViBuCdJgiOkT2Y) - Gate Smashers
+* [DBMS Placements Series 2022](https://www.youtube.com/playlist?list=PLDzeHZWIZsTpukecmA2p5rhHM14bl2dHU) - CodeHelp by Babbar
+
+
 ### DevOps
 
 * [DevOps Bootcamp](https://www.youtube.com/playlist?list=PL9gnSGHSqcnoqBXdMwUTRod4Gi3eac2Ak) - Kunal Kushwaha