对多个 LIKE 字符串进行分组

Question

数据：

2015478 warning occurred at 20201403021545
2020179 error occurred at 20201303021545
2025480 timeout occurred at 20201203021545
2025481 timeout occurred at 20201103021545
2020482 error occurred at 20201473021545
2020157 timeout occurred at 20201403781545
2020154 warning occurred at 20201407851545
2027845 warning occurred at 20201403458745

在上面的数据中，我感兴趣的字符串有warning、error和timeout这3种 我们可以有一个查询，它将按字符串分组并给出如下所示的出现次数

输出：

timeout 3
warning 3
error 2

我知道我可以编写单独的查询来单独查找计数。但对单个查询感兴趣 谢谢

Answer 1

您可以为此使用过滤聚合：

select count(*) filter (where the_column like '%timeout%') as timeout_count, 
       count(*) filter (where the_column like '%error%') as error_count, 
       count(*) filter (where the_column like '%warning%') as warning_count
from the_table;

这将返回三列中的计数，而不是您指示的三行。

如果您确实需要在单独的行中使用它，您可以使用regexp_replace() 来清理字符串，然后按此分组：

select regexp_replace(the_column, '(.*)(warning|error|timeout)(.*)', '\2') as what,
       count(*) 
from the_table
group by what;

Answer 2

请使用下面的查询，不要使用STRPOS对值进行硬编码

select val, count(1) from
(select substring(column_name ,position(' ' in (column_name))+1,
length(column_name) - position(reverse(' ') in reverse(column_name)) - 
position(' ' in (column_name))) as val from  matching) qry
group by val;  -- Provide the proper column name

演示：

Answer 3

如果您想在单独的行上进行此操作，您还可以使用横向连接：

select which, count(*)
from t cross join lateral
     (values (case when col like '%error%' then 'error' end),
             (case when col like '%warning%' then 'warning' end),
             (case when col like '%timeout%' then 'timeout' end)
     ) v(which)
where which is not null
group by which;

另一方面，如果您只是想要第二个词——但不想硬编码值——那么你可以使用：

select split_part(col, ' ', 2) as which, count(*)
from t
group by which;

Here 是一个 dbfiddle。