Raid 5 and XOR

Hi, Today while talking with a friend he mentioned about using a RAID 5 on disks. Since I am not experienced with RAID structures, after the conversation, I started to read about RAID 5. of course I know what RAID is and basically how it works but don’t have information about all types. so while

Sequential ID column without gap!

Hello, A customer is asking to you generate order numbers one by one and without gap! What an unpleasant request isn’t it? if you are not familiar to databases then you might think that this request is logical but it is not. So your customer asked for this and you decided to develop your code