BigQuery：当表达式要从同一列但条件不同时进行计数时的情况

Question

I have a table with 2 columns as below:

Col 1    | col_stats
Field 1  |   open
Field 2  |   close
Field 1  |   close
Field 1  |   open

I want the ouput to be as :

Col1    | cnt_open | Cnt_close
Field 1 |  2          | 1             
Field 2 |  0          | 1             

**I wrote a query **

select col 1, count(case when col_stats= 'open' then 1 else 0 END) cnt_open,
count (case when col_stats= 'close' then 1 else 0  END ) cnt_close 
from `project.dataset.tablename`
group by col1

Resultant output from above query is incorrect:

Col1    | cnt_open | Cnt_close  
Field 1 |  2          | 2             
Field 2 |  1          | 1  

Can somebody let me know why the output is giving incorrect result for count even after case condition is applied?

Answer 1

Use countif() :

select col1, countif(col_stat = 'open') as num_opens, countif(col_stat = 'closed') as num_closes
from t
group by col1;

In SQL count() counts the number of non- NULL values. Your code would work with sum() . But countif() is simpler and clearer.

Answer 2

Use null instead of 0 :

select col1, count(case when col_stats= 'open' then 1 else null END) cnt_open,
count (case when col_stats= 'close' then 1 else null  END ) cnt_close 
from `project.dataset.tablename`
group by col1