各位老鸟,能不能根据你们的经验说说索引,别名有什么用处

Question

index can increse the searching speed. sometimes 20 times faster.alias just shorten the sql statement.

Answer 1

用别名可以使sql语句更清晰，书写更简洁、方便。

Answer 2

alias:suppose you have two tables.
T001_user_information(id, firstname,secondname,...)
T002_business_information(id, firstname, secondname, ...)now select id when user and business has the same firstname and secondname, just for testing.if you do not use alias, it would beselect T001_user_information.id, T002_business_information.id
from T001_user_information, T002_business_information
where T001_user_information.firstname=T002_business_information.firstname
  and T001_user_information.secondname=T002_business_information.secondnameif you use alias, it would beselect t1.id, t2.id
from T001_user_information t1, T002_business_information t2
where t1.firstname=t2.firstname
  and t1.secondname=t2.secondnamejust a bit short. nothing else