比较组中具有特定值的行PostgreSQL

问题描述

当5或9不存在时，我需要一个空值(或另一个标志)

when 5 or 9 does not exist, i need a null value (or another flag)

我有3栏.部分，状态和名称.在SECTION中，最多可包含10行(状态1至10).我必须在SECTION中比较STATUS 5和9的NAME值.然后指出每个部分的两个名称(用于状态5和状态9)是否相同.

I have 3 columns. SECTION, STATUS and NAME. Within a SECTION there are a maximum of 10 rows (STATUS 1 to 10). I have to compare the value of NAME for STATUS 5 and 9 within a SECTION. AND then indicate if those 2 NAMES (for STATUS 5 and 9) are the same for each SECTION.

部分状态名称1 51 61 9 b2 4 c2 5天2 9天2 10天3 5 e3 10 e

section status name1 5 a1 6 a1 9 b2 4 c2 5 d2 9 d2 10 d3 5 e3 10 e

所需的输出

Section equalnames
1      no
2      yes
3      null/flag

推荐答案

我将使用布尔值而不是字符串，而仅使用带过滤的聚合:

I would use a boolean instead of strings and just use aggregation with filtering:

select group, min(name) = max(name) as names_equal_flag
from t
where status in (5, 9)
group by group;

请注意， group 对于列来说确实是个坏名字，因为它是一个SQL关键字.我假设您在实际数据中使用一个更合适的名称.

Note that group is a really bad name for a column because it is a SQL keyword. I assume you have a more appropriate name in your actual data.

如果需要字符串，可以使用 case :

If you want a string, you can use case:

select group,
       (case when min(name) = max(name) then 'yes' else 'no' end) as names_equal_flag
from t
where status in (5, 9)
group by group;

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