The PostgreSQL MAKE_DATE
function is used to create a date from year, month, and day fields. This function is essential for constructing date values from individual components, which can be useful in various date-based calculations and data manipulations.
MAKE_DATE(year int, month int, day int)
The MAKE_DATE
function has the following components:
year
: The year component of the date (negative years signify BC).month
: The month component of the date.day
: The day component of the date.Let's look at some examples of PostgreSQL MAKE_DATE
function queries:
SELECT MAKE_DATE(2013, 7, 15) AS constructed_date;
This query creates a date from the year 2013, month 7, and day 15, resulting in '2013-07-15'.
SELECT MAKE_DATE(-44, 3, 15) AS constructed_date;
This query creates a date from the year 44 BC, month 3, and day 15, resulting in '0044-03-15 BC'.
SELECT id, name, MAKE_DATE(year, month, day) AS birthdate
FROM people;
This query retrieves the id
, name
, and constructs a birthdate from the year, month, and day columns for each row in the people
table.
Let's go through a complete example that includes creating a table, inserting data, and using the MAKE_DATE function to construct dates from individual components.
This step involves creating a new table named people
to store people's data, including their birthdate components.
CREATE TABLE people (
id SERIAL PRIMARY KEY,
name TEXT,
year INT,
month INT,
day INT
);
In this example, we create a table named people
with columns for id
, name
, year
, month
, and day
.
This step involves inserting some sample data into the people
table.
INSERT INTO people (name, year, month, day)
VALUES ('Alice', 1990, 5, 20),
('Bob', 1985, 12, 3),
('Charlie', 2000, 7, 15);
Here, we insert data into the people
table.
This step involves using the MAKE_DATE()
function to construct dates from the individual components in the people
table.
Construct birthdate from year, month, and day columns:
SELECT id, name, MAKE_DATE(year, month, day) AS birthdate
FROM people;
This query constructs the birthdate from the year, month, and day columns for each row in the people
table.
The PostgreSQL MAKE_DATE()
function is a fundamental tool for constructing date values from individual year, month, and day components. Understanding how to use the MAKE_DATE()
function and its syntax is essential for accurate date construction in PostgreSQL databases.