Subject I’d like to discuss today is SQLServer Union. Union and Union All are two of the SQLServer’s syntax. What is the difference? Let’s analyze what’s your query requirement.
Let’s say I have 2 tables, Students_A and Soccer_Team. The rules are one or more students could join to the soccer_team and a Soccer_Team member are students and free-school student. Free-school student could join the soccer team, with a note if he achieve success in his team, he could get scholarship to continue his study. So it could be students in soccer_team don’t exist in Students_A (if he doesn’t achieve success).
