Question

我想将我的一个表格中的数据插入到另一个表格中这是我填写的表格：

 Act (
 id  INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
 birth_date DATETIME,
 death_date DATETIME,
 place VARCHAR(20)  
 );

在此表中，某些值为NULL - 例如，如果它是一个出生行为，则death_date为NULL。

这是我要将数据传输到的表格：

 Population_Growth (
 id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
 number_of_births INT,
 number_of_deaths INT,
 place VARCHAR(20),
 time DATE
 );

最后，我希望此表能够显示同一地点和同一天的死亡人数和出生人数。至于出生和死亡的数量，我会做这样的事情：

INSERT INTO Population_Growth (number_of_births, number_of_deaths) VALUES 
((COUNT (birth_date) FROM Act WHERE birth_date IS NOT NULL)), 
((COUNT (death_date) FROM Act WHERE death_date IS NOT NULL));

但我不知道如何将其与相应的时间和日期联系起来。

Answer 1

获取指定结果的一种方法是这样的查询：

SELECT c.place
     , c.time
     , SUM(c.count_births) AS number_of_births
     , SUM(c.count_deaths) AS number_of_deaths
  FROM (
         SELECT b.place
              , DATE(b.birth_date) AS `time`
              , SUM(1) AS count_births
              , SUM(0) AS count_deaths
           FROM Act b
          WHERE b.birth_date IS NOT NULL
          GROUP BY b.place, DATE(b.birth_date)
          UNION ALL
         SELECT d.place
              , DATE(d.death_date) AS `time`
              , SUM(0) AS count_births
              , SUM(1) AS count_deaths
           FROM Act d
          WHERE d.death_date IS NOT NULL
          GROUP BY d.place, DATE(d.death_date)
       ) c
  GROUP BY c.place, c.time

要将其转换为插入，请在SELECT前面加上：

INSERT INTO Population_Growth (place, `time`, number_of_births, number_of_deaths)

<强>后续

上面的查询将DATETIME列转换为DATE数据类型（通过截断时间部分。）

要按年份和月份获取摘要，但仍作为有效分配到DATE列的表单，一个选项是替换所有表达式：

DATE(b.birth_date)
DATE(d.death_date)

（在上面的查询中）包含以下表达式：

DATE_FORMAT(b.birth_date,'%Y-%m-01')
DATE_FORMAT(d.death_date,'%Y-%m-01')

新表达式将从DATETIME列中提取年份和月份，并将day组件设置为该月的第1个。

Answer 2

如果我理解正确，您希望从两个日期列中获取非NULL值的计数。以下是获取摘要的一种方法：

select place, d,
       (select count(*) from act where act.birth_date = pd.d and act.place = pd.place) as births,
       (select count(*) from act where act.death_date = pd.d and act.place = pd.place) as deaths
from (select place, birth_date as d from act union
      select place, death_date from act
     ) pd;

然后您可以通过执行以下操作将其放入population_growth：

INSERT INTO Population_Growth(place, time, number_of_births, number_of_deaths) 
    select place, d,
           (select count(*) from act where act.birth_date = pd.d and act.place = pd.place) as births,
           (select count(*) from act where act.death_date = pd.d and act.place = pd.place) as deaths
    from (select place, birth_date as d from act union
          select place, death_date from act
         ) pd;

将值从一个表插入另一个MySQL

2 个答案: