时序数据库 概览

1、常见时序数据库
参考：
https://www.influxdata.com/time-series-database/#ranking
https://db-engines.com/en/

2、时序数据库
    <1> riakTS (分布式 时序数据库)
    <2> 特点
    设置过期类型：http://docs.basho.com/riak/ts/1.5.2/using/deleting-data/
    查询：
        select/IS[NOT]NULL/：http://docs.basho.com/riak/ts/1.5.2/using/querying/select/
        group by(支持多字段排序): http://docs.basho.com/riak/ts/1.5.2/using/querying/select/group-by/
        聚合(COUNT(),SUM(),MEAN(),AVG(),STDDEV(),STDDEV_SAMP(),STDDEV_POP()):http://docs.basho.com/riak/ts/1.5.2/using/querying/select/aggregate-functions/
        ordery by : http://docs.basho.com/riak/ts/1.5.2/using/querying/select/order-by/
        limit: http://docs.basho.com/riak/ts/1.5.2/using/querying/select/order-by/#limit-results
        off-results(跳过第几个后获取): http://docs.basho.com/riak/ts/1.5.2/using/querying/select/order-by/#offset-results
        Arithmetic Operations(算术操作)：http://docs.basho.com/riak/ts/1.5.2/using/querying/select/arithmetic-operations/        
        删除：与关系型数据库类似
        描述表结构：http://docs.basho.com/riak/ts/1.5.2/using/querying/describe/
        表状态：http://docs.basho.com/riak/ts/1.5.2/using/querying/show-tables/
        表创建语句：http://docs.basho.com/riak/ts/1.5.2/using/querying/show-create-table/
        explain：查看SQL执行效率