MySQL 表一般情况下是不是需要主键,没有主键查询是不是低效一点 - V2EX
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tanteng
V2EX    MySQL

MySQL 表一般情况下是不是需要主键,没有主键查询是不是低效一点

  •  
  •   tanteng
    tanteng Jun 11, 2015 3486 views
    This topic created in 4012 days ago, the information mentioned may be changed or developed.

    做一个统计功能,连两张统计表,一张按天统计数据,一张存每个小时的数据,这两张表都没设主键,那么程序查的时候,各种select语句会不会低效一点,是否应该加上主键,数据多加上索引呢?

    3 replies    2015-06-11 20:14:21 +08:00
    20150517
        1
    20150517  
       Jun 11, 2015 via Android
    按小时统计,一天就24小时,24条rows,要毛index

    按天的,你没主健那就scan表了,是会慢
    iyangyuan
        2
    div class="sep3"> iyangyuan  
       Jun 11, 2015 via iPhone
    对于innodb引擎而言,如果没有显式声明主键,MYSQL会自动生成一个主键
    billlee
        3
    billlee  
       Jun 11, 2015
    一般情况都需要主键。像统计表这种有意义明确的 key 的,就直接作为主键就行了。
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