Database mysql Foundation

One 、 Database engine ：InnoDB( You can add foreign keys and support transaction operations )
Two 、 The purpose of quotation is to query quickly , The bottom layer of the database is B+ Trees , A node contains index values and pointers to physical storage addresses .
3、 ... and 、 The consistency of transactions and adding some database read-write locks ;
Four 、left join,right join Left and right connection
5、 ... and 、sql Storage statements are similar to java Methods , Also have if/else Such statements