显示PostgreSQL中多个列的月度总计

我希望看到在给定日期范围内，今年与去年每月就诊的首次检查患者数量，并将其与相同日期范围内每月就诊的患者总数进行比较

我可以按如下方式设置首次检查患者：

select case EXTRACT(month FROM patient_info.firstexam)
    when 1 then '01 - January'
    when 2 then '02 - February'
    when 3 then '03 - March'
    when 4 then '04 - April'
    when 5 then '05 - May'
    when 6 then '06 - June'
    when 7 then '07 - July'
    when 8 then '08 - August'
    when 9 then '09 - September' 
    when 10 then '10 - October'
    when 11 then '11 - November'
    when 12 then '12 - December'
end as month,
sum(case when patient_info.firstexam >= '2013-01-01' AND patient_info.firstexam <= '2013-12-31' then 1 else 0 end) thisyear,
sum(case when patient_info.firstexam >= '2012-01-01' AND patient_info.firstexam <= '2012-12-31' then 1 else 0 end) lastyear

from patient_info WHERE (patient_info.firstexam >= '2013-01-01' AND patient_info.firstexam <= '2013-12-31' OR patient_info.firstexam >= '2012-01-01' AND patient_info.firstexam <= '2012-12-31') 

GROUP BY month
ORDER BY month

选择病例摘录（患者信息第一次检查的月份）
当1然后是'01-一月'
当2时，然后是'02-二月'
3月3日，然后是'03-3月'
当4时，然后是'04-April'
5月5日，然后是5月5日
6月6日，然后是'06-6月'
7时，然后是'07-7'
8时，然后是'08-8月'
9时，然后是'09-9'
10时，然后是“10月10日”
11月11日，然后是“11月11日”
12月12日，然后是“12月12日”
月底，
总和（当患者信息第一次检查>='2013-01-01'和患者信息第一次检查='2012-01-01'和患者信息第一次检查='2013-01-01'和患者信息第一次检查='2012-01-01'和患者信息第一次检查='2013-01-01'和患者信息第一次检查='2012-01-01'和患者信息第一次检查='2013-01-01'和患者信息第一次检查='2012-01-01'和患者信息第一次检查='2012-01-01'ent_info.lastexam

不知道为什么，但是第一栏（今年）是唯一给出正确计数的列。所有其他列的实际数字都低于上面返回的代码。例如，上面的代码返回的是1月148、230、360、238，但当我单独搜索时，实际数字应该是148、179、275、203。知道错误可能来自何处吗？@kipsoft什么时候我单独搜索查询？从患者信息中选择firstexam，其中firstexam介于“2013-01-01”和“2013-01-31”之间（我使用为计数返回的记录数），然后我只是将日期范围从2013年更改为2012年，并将字段从firstexam更改为lastexam以获得其他结果。@kipsoft Ok检查新版本。我有一个问题一直困扰着我。我不是从patient_info表中计算lastexam，而是尝试从transactions表中计算唯一的患者就诊次数。Firstexam数字可以，但并非所有用户都会在每笔交易中更新LastCheck列-因此我需要修改此值，以便每个月的总患者数是该月的总患者就诊数。这通常会算作交易总数，但是，有些患者可能会在一天内收到两张发票，而这只会是共同的未测试为一次患者就诊）。
select case EXTRACT(month FROM patient_info.lastexam)
    when 1 then '01 - January'
    when 2 then '02 - February'
    when 3 then '03 - March'
    when 4 then '04 - April'
    when 5 then '05 - May'
    when 6 then '06 - June'
    when 7 then '07 - July'
    when 8 then '08 - August'
    when 9 then '09 - September' 
    when 10 then '10 - October'
    when 11 then '11 - November'
    when 12 then '12 - December'
end as month,
sum(case when patient_info.lastexam >= '2013-01-01' AND patient_info.lastexam <= '2013-12-31' then 1 else 0 end) totalthisyear,
sum(case when patient_info.lastexam >= '2012-01-01' AND patient_info.lastexam <= '2012-12-31' then 1 else 0 end) totallastyear

from patient_info WHERE (patient_info.lastexam >= '2013-01-01' AND patient_info.lastexam <= '2013-12-31' OR patient_info.lastexam >= '2012-01-01' AND patient_info.lastexam <= '2012-12-31') 

GROUP BY month
ORDER BY month

select
    to_char(('2012-' || m || '-01')::date, 'Month'),
    thisyear, lastyear, totalthisyear, totallastyear
from (
    select
        extract(month from m) as m,
        sum(case
            when firstexam between '2013-01-01' and '2013-12-31' then firstexam_count
            else 0 end
        ) as thisyear,
        sum(case
            when firstexam between '2012-01-01' and '2012-12-31' then firstexam_count
            else 0 end
        ) as lastyear,
        sum(case
            when lastexam between '2013-01-01' and '2013-12-31' then lastexam_count
            else 0 end
        ) as totalthisyear,
        sum(case
            when lastexam between '2012-01-01' and '2012-12-31' then lastexam_count
            else 0 end
        ) as totallastyear
    from
        generate_series (
            '2012-01-01'::date, '2013-12-31', '1 month'
        ) g(m)
        left join (
            select count(*) as firstexam_count, date_trunc('month', firstexam) as firstexam
            from patient_info
            where firstexam between '2012-01-01' and '2013-12-31'
            group by 2
        ) pif on firstexam = m
        left join (
            select count(*) as lastexam_count, date_trunc('month', lastexam) as lastexam
            from patient_info
            where lastexam between '2012-01-01' and '2013-12-31'
            group by 2
        ) pil on lastexam = m
    group by 1
) s
order by m