Get the fastest difference for MySQL two tables

MySQL is nothing more than a subquery and two ways of connecting.

The first table is Table1, the second is table2, and Table1 contains table2.

SQL is:

1 //Sub-query2 SelectTable1.id fromtable13   where  not exists 4(Select 1  fromtable25      whereTable1.id=table2.id6     );7  8 //External Connection9 SelectTable1.id fromtable1Ten    Left Jointable2 One    onTable1.id=table2.id A whereTable2.id is NULL;

There are similar examples in high-performance MySQL, see "When a correlated subquery is good" section. It gives the data, the outer connection to be fast.

Also, to be the fastest, it is best to do a difference between the primary keys of the two tables, so that only the index is overwritten, it will be faster.

Get the fastest difference for MySQL two tables