MySQL optimization essentials (i)

It is important to note that a function is used in an SQL statement because it is possible that each statement will be called, even if each record in the table is called.

Pay attention to the conversion, will consume a lot of performance, even the string of encoding different, there will be very large consumption

The count (*) function of three MyISAM, the number of records will be removed from the table information directly.

Conditions for four constant table:

1 empty table and a table with only one record.

2 the query condition in query statement exactly matches the clustered index or Unquie

Pros: Such tables are always faster than other tables.

MySQL optimization essentials (i)