Brief Introduction to database creation view Efficiency

A Brief Introduction to the efficiency of creating a database view the main purpose of creating a view is to facilitate data query, but not to improve the query efficiency. To improve the efficiency, you can only optimize it through other methods, for example, creating an index. The following statement proves that the average data is queried by day. The data volume is 0.58 million select avg (ave_value) ave_value, to_date (CONCAT (to_char (create_time, 'yyyy-mm-dd'), '00:00:00 '), 'yyyy-mm-dd hh24: mi: ss') create_time from PDB_NWD_CPUM_D group by to_char (create_time, 'yyyy-mm-dd'); time consumed: create a view under 0.422 seconds and create view PDB_NWD_CPUM_D_DAY as select avg (ave_value) ave_value, to_date (CONCAT (to_char (create_time, 'yyyy-mm-dd'), '00:00:00 '), 'yyyy-mm-dd hh24: Mi: ss ') create_time from PDB_NWD_CPUM_D group by to_char (create_time, 'yyyy-mm-dd'); after the view is created, we query this view: select ave_value, create_time from PDB_NWD_CPUM_D_DAY; the query efficiency was not improved when it took more than 0.429 seconds to run several times. Of course, if you create a view for multiple tables, it will reflect the advantages of the view-convenience.