Inserting values from one table to another MySQL

Question

I want to insert the data from one of my tables to another This is the filled table that I have:

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

In this table some of the values are NULL - for example if it's a birth act then death_date is NULL.

And this is the table I want to transfer data into:

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

In the end I would like this table to show number of deaths and number of births in the same place and the same date. As for numbers of births and deaths I would do something like this:

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));

However I don't know how to relate it with the corresponding time and date.

Answer 1

One way to get the specified result would be a query like this:

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

To turn that into an insert, precede the SELECT with:

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

---

FOLLOWUP

The query above casts the DATETIME columns to a DATE datatype (by truncating the time portion.)

To get the summary by year and month, but still as a form valid for assignment to a DATE column, one option is to replace all of the expressions:

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

(in the query above) with these expressions:

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

The new expressions will extract the year and month from the DATETIME column, and set the day component to the 1st of the month.

Answer 2

If I understand correctly, you want to get the count of non-NULL values from two date columns. Here is one approach to getting the summary:

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;

You can then put this into population_growth by doing:

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;