Here is the process to backup your wordpress blog using phpMyAdmin:

1. Log into phpMyAdmin on your server

2. From the main login screen, select ‘Databases’

3. Now click the name of your database - or your WordPress database if you have several databases.

4. The next screen will show you all the tables inside your WordPress database.
Ignore those, and click the ‘Export’ tab on the top set of tabs.

5. Look at the left box at the top of the Export section. All the tables in the database you selected are in that box.

* If you’re using other program, then choose only those tables that correspond to your wordpress install. They will be the ones with that start with “wp_” or whatever ‘table_prefix’ you specified in your ‘wp-config.php’ file.
* If you only have your WordPress blog installed, in the left column, click ‘Select All’.
6. Ensure that the SQL button is selected too. (Image#5)
* The SQL section
* Tick the following boxes: Structure, ‘Add DROP TABLE’, ‘Add AUTO_INCREMENT’ and ‘Enclose table and field names with backquotes’
7. The DATA section

* Leave the boxes inside this section un ticked, but make sure to keep the checkbox next to the “DATA” heading checked.
8. Tick the ‘Save as file’ option, and leave the template name alone.
For now, select ‘None’ for compression.
9. Now click ‘Go’ and you should be prompted for a file to download. Save the file to your computer. (Image#6)
Depending on the database size, this may take a few moments.
10. Once that download is complete, check the ‘zipped’ option, click ‘Go’, and download the next file.
You can also download a backup in each of the compression formats. Your choice.
11.  Now you’ve finished up the  back up process  of your database.

Point to remember: Even you’ve not back up your image, all your posts and comments with specific date are now safe.