Question

我有一个现有的table1，其中包含＆＃34; account＆＃34;，＆＃34; tax_year＆＃34;和其他领域。当CONCAT（account，tax_year）的频率为1并满足WHERE子句时，我想创建一个table2，其中包含来自table1的记录。

例如，如果table1如下所示：

account year
aaa 2014
ddd 2015

表2应为：

DROP TABLE IF EXISTS table1;
CREATE table2 AS
SELECT 
    account::text, 
    tax_year::text,
    building_number,
    imprv_type,
    building_style_code,
    quality,
    quality_description,
    date_erected,
    yr_remodel,
    actual_area,
    heat_area,
    gross_area,
    CONCAT(account, tax_year) AS unq
FROM table1
WHERE imprv_type=1001 and date_erected>0 and date_erected IS NOT NULL and quality IS NOT NULL and quality_description IS NOT NULL and yr_remodel>0 and yr_remodel IS NOT NULL and heat_area>0 and heat_area IS NOT NULL
GROUP BY account, 
    tax_year,
    building_number,
    imprv_type,
    building_style_code,
    quality,
    quality_description,
    date_erected,
    yr_remodel,
    actual_area,
    heat_area,
    gross_area,
    unq
HAVING COUNT(unq)=1;

这是我的剧本：

struct num* deleteCell(struct num* point, int numdelete) {
  if (point == NULL) {
     return NULL;
  }

  if (point->number == numdelete) { 
    num* tempdelete = point->pNext;
    free(point);
    return deleteCell(tempdelete, numdelete);
  }

  point->pNext = deleteCell(point->pNext, numdelete);
  return point;
}

我花了两天时间，但仍然无法弄清楚如何做到正确。谢谢你的帮助！

Answer 1

COUNT() = 1相当于NOT EXISTS(another with the same key fields)：

SELECT 
    account, tax_year
    -- ... maybe more fields  ...
FROM table1 t1
WHERE NOT EXISTS ( SELECT *
    FROM table1 nx
    WHERE nx.account = t1.account  -- same key field(s)
    AND nx.tax_year = t1.tax_year
    AND nx.ctid <> t1.ctid         -- but a different row!
    );

注意：我用复合匹配键替换了COUNT(CONCAT(account, tax_year)关键字段的连接。

Answer 2

在(account, tax_year)中使用table1对的正确方法：

select account, tax_year
from table1
where imprv_type=1001 -- and many more...
group by account, tax_year
having count(*) = 1;

所以你应该尝试：

create table table2 as
select * 
from table1
where (account, tax_year) in (
    select account, tax_year
    from table1
    where imprv_type=1001 -- and many more...
    group by account, tax_year
    having count(*) = 1
    );

如何在PostgreSQL中使用Count作为标准

2 个答案: