For posting/updating/showing in your blog, research these SQL commands: SELECT, UPDATE, INSERT, DELETE
For getting info from your DB with PHP: mysql_* functions (using SQL)
For showing them: while, mysql_fetch_assoc
The PHP and MySQL manuals are not too complicated to read. You will find all you need there.
If you still don't know the basics of PHP, then read the language reference in the PHP manual.
Also, in the PHP manual:
Read the notes! Some stuff are not entirely docummented or clear enough, so the user notes sometimes help (be aware, that some might be misleading or have outdated/wrong information!).
php.net /
mysql.com
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