This is personal study note Copyright and original reference: https://www.youtube.com/watch?v=7UpsG6_HoI0&list=PLVsNizTWUw7HhYtI-4GGmlJ5yxNdwNI_X ================================================================================ ================================================================================ use between and ================================================================================ simpler by using where in () ================================================================================ % wildcard _ wildcard ================================================================================ Use sub query for super query ================================================================================ In drag sentence, it must have one number, in that case, it's 2 numbers which are returned from that sub query To resolve it, use any ================================================================================ order by height --> order by name "order by" should be avoided in use due to high computational cost unless it's inevitably required ================================================================================ remove duplicates in the result (useful) ================================================================================ quiry 5 employees who have worked for longest period This shows 300000 records By using Limit, you can cut the result longest employeement period: 100 to 105 employees ================================================================================ Create table It's kind of "copy table buyTbl to buyTbl2"