fixing link to SQL file

Documentation/Database-Schema.md

@@ -7,7 +7,7 @@ Note that some of this documentation might be incorrect or out of date.
 If you see any problems, please feel free to open an issue or issue
 a pull request to correct the issue.
 
-Please see the [create_tables.sql](/server/sql_schema/create_tables.sql) file for the
+Please see the [create_tables.sql](../server/sql_schema/create_tables.sql) file for the
 underlying SQL used to create the database tables.
 
 ---