Vertica SQL 用于按列获取数据

Question

enter image description hereVertica SQL 用于按列获取数据，其中在具有不同条件的单个表中支持多个计数

1. select COUNT(*) as x from  WORLDPOP
2. SELECT COUNT(*) as y FROM WORLDPOP WHERE COUNTRY LIKE '%i%'

操作

x   y
10  2

Answer 1

你想要条件聚合：

select count(*) as x,
       sum(case when COUNTRY LIKE '%i%' then 1 else 0 end) as y
from WORLDPOP;

Answer 2

条件聚合是要走的路。我更喜欢这种在 Postgres 兼容数据库（包括 Vertica）中可用的较短语法：

select count(*) as x,
       sum( (country like '%i%')::int ) as y
from WORLDPOP;