Postgresql 动态统计某一列的某一值出现的次数实例

 

这篇文章主要介绍了Postgresql 动态统计某一列的某一值出现的次数实例,具有很好的参考价值,希望对大家有所帮助。一起跟随小编过来看看吧。

实例解析:

select to_char(log.date, ‘yyyy-MM-dd HH24’) as hour,
  log.exten, sum(case log.grade when ‘1’ then 1 else 0 end) as “1”,
  sum(case log.grade when ‘2’ then 1 else 0 end) as “2”,
  sum(case log.grade when ‘3’ then 1 else 0 end) as “3”,
  sum(case log.grade when ‘4’ then 1 else 0 end) as “4”,
  sum(case log.grade when ‘5’ then 1 else 0 end) as “5”,
  log.direction from iface_satisfaction_investigation as log
where log.date >= ‘2017-08-03 00:00:00’ and log.date < ‘2017-08-04 00:00:00’
group by hour,log.exten,log.direction order by hour,log.exten,log.direction asc

 

to_char:用于查询时间格式化,to_char(log.date, ‘yyyy-MM-dd HH24’),大致的结果是:2017-08-03 13

sum():毫无疑问是用来计算总和的。

sum(case log.grade when ‘1’ then 1 else 0 end) 是计算什么呢?

他的意思就是:

计算grade这个列的值为1的时候有多少行,后面的sum(……)就类推了。

其他的也没有什么好讲的了

补充:PostgreSQL常用的统计信息

我就废话不多说了,大家还是直接看代码吧~

/*计算表的空间大小*/
select oid,table_schema as “模式”,
 table_name as “表名”,
 row_estimate::bigint as “表中的行数(估计值)”,
 pg_size_pretty(total_bytes) as “总大小”,
  pg_size_pretty(table_bytes) as “表大小”,
 pg_size_pretty(index_bytes) as “索引大小”,
  pg_size_pretty(toast_bytes) as “toast表总大小” 
from (
 select *, total_bytes-index_bytes-coalesce(toast_bytes,0) as table_bytes
  from (
   select
    c.oid,
    nspname as table_schema,
    relname as table_name,
    c.reltuples as row_estimate,
    pg_total_relation_size(c.oid) as total_bytes,
    pg_indexes_size(c.oid) as index_bytes,
    pg_total_relation_size(reltoastrelid) as toast_bytes
   from pg_class c
   left join pg_namespace n on n.oid = c.relnamespace
   where relkind = ‘r’
 ) t1
) t2 order by 2,3;
/*统计用户表信息*/
select
 schemaname as “模式”,
 relname as “表名”,
 seq_scan as “顺序扫描的次数”,
 seq_tup_read as “顺序扫描获取活动行的数量”,
 idx_scan as “索引扫描次数”,
 idx_tup_fetch as “索引扫描获取活动行的数量”,
 n_tup_ins as “累计插入的行数”,
 n_tup_upd as “累计更新的行数(包含HOT 更新的行)”, 
 n_tup_del as “累计删除的行数”,
 n_live_tup as “当前活动行估计数量”,
 n_dead_tup as “当前死亡行的估计数量”,
 n_mod_since_analyze as “最后一次分析后被修改的行估计数量”,
 last_vacuum as “上次被手动清理的时间(不统计VACUUM FULL)”,
 last_autovacuum as “上次自动清理的时间”,
 last_analyze as “上次手动分析的时间”,
 last_autoanalyze as “上次自动清理分析的时间”,
 vacuum_count as “手动清理的次数”,
 autovacuum_count as “自动清理的次数”,
 analyze_count as “手动分析的次数”,
 autoanalyze_count as “自动分析的次数”,
 pg_size_pretty(pg_table_size(relid)) as “表大小(不包含索引)”
from pg_stat_user_tables
order by 1;
/*统计用户表IO信息*/
select
 schemaname as “模式”,
 relname as “表名”,
 heap_blks_read as “读取的磁盘块数量”,
 heap_blks_hit as “缓冲区命中数量”,
 idx_blks_read as “表上所有索引读取的磁盘块数”,
 idx_blks_hit as “表上的所有索引缓冲区命中数量”,
 toast_blks_read as “TOAST表(如果有)读取的磁盘块数”,
 toast_blks_hit as “TOAST表(如果有)缓冲区命中数量”,
 tidx_blks_read as “TOAST表索引(如果有)读取的磁盘块数”,
 tidx_blks_hit as “TOAST表索引(如果有)缓冲区命中数量”
from pg_statio_user_tables
order by 1;
/*统计用户索引信息*/
select
 indexrelid,
 schemaname as “模式”,
 relname as “索引所在的表名称”,
 indexrelname as “索引名称”,
 idx_scan as “索引扫描次数”,
 idx_tup_read as “索引扫描返回的索引项数量”,
 idx_tup_fetch as “简单索引扫描获取的活动行数量”,
 pg_size_pretty(pg_relation_size(indexrelid)) as “索引大小”
from pg_stat_user_indexes
order by 1,2;
/*追踪函数,需要打开track_functions参数(默认关闭)*/
select * from pg_stat_user_functions;

文章

①本站所有CMS源码、杰奇CMS模板、PTCMS源码模板、YGBOOK源码模板、帝国CMS源码模板等仅用于学习和交流,勿用于商业。
②本站资源有安装及使用文档,安装使用请自行探索,如您对购买的程序或是模板无法胜任安装工作,请点击付费安装。
③本站资源来源网络或者用户投稿,切勿私自传播于网络,否则将追究法律责任。且仅供学习交流之用,如有侵权请联系删除。
④如果资源失效或下载链接错误请联系站长。
悟空资源网 » Postgresql 动态统计某一列的某一值出现的次数实例

发表评论