One, background
Query all data, time-consuming, consuming memory directly from the database, changed some data paging query
Second, the conventional query
1. mysql: limit start data from the m, n data query
select * from table limit m,n
2. sql server: top + subqueries
3. Principle: From the first record of the database to begin scanning
More backward, i.e. the greater the m, the slower the query
The more data queries, that n, the more slow query
Third, the use of sub-query optimization, first find a id, then the limit according to id, identify data
Fourth, according to defined optimization do id, the id as a condition where
Fifth, optimize the use of temporary table, first find out all the id, and then find out in the trial data