Merge pull request #3 from PhamQuocTien132/develop

Develop
optimize code for PHP
remove "AS" in sql JOIN syntaxes for the table
change UNIX_TIMESTAMP by NV_CURRENTTIME in SQL
optimize structure for table database
Remover "NULL" in sql insert with Primary AUTO_INCREMENT
Remove LITMIT 1 in SQL
Merge pull request #67 from vuthao/develop

Change SQL code