Introduction to PostgreSQL age() Function
PostgreSQL age() function is used to calculate the age between two dates, it will return the number of years, days, and months between the two different dates. Age function in PostgreSQL will accept the two arguments as date timestamp and return the calculated difference between two different dates. The age function in PostgreSQL is to perform the two different calculations depending on which parameter we have used with age function. Age function is very important and useful in PostgreSQL to subtract the arguments and produce the symbolic result which was used in months and years.
Syntax
Below is the syntax of age function in PostgreSQL:
age (timestamp, timestamp)
OR
age(date1, date2)
OR
age (timestamp)
Parameters
Below is the parameter description syntax of age function in PostgreSQL:
Age: This is a function in PostgreSQL used to return the interval type. The age function basically accepts the two-parameter to return the result. Age function in PostgreSQL will accept the timestamp value as its input parameter.
Timestamp: Timestamp in PostgreSQL age function is defined as accepting the timestamp arguments. We have used two timestamps with age function, two arguments are used to subtract the second argument from the first argument.
Date 1 and Date 2: This is the same as timestamp which we have used with age function in PostgreSQL. It will work the same as timestamp work in age function. We can use the first date as the current date.
How does PostgreSQL age() function works?
Below is the working of age function in PostgreSQL:
We are using age function in PostgreSQL to return the year, month, and day as result from two timestamps. For using age function in PostgreSQL we need to pass two arguments. The first argument as a timestamp or current date and the second argument is a timestamp. We also use the current date as the first timestamp in the first argument. The below example shows that we are using the current date as the first argument with age function in PostgreSQL. If we want to return the current age of person then we are using the current date as the first argument with age function.
Code:
SELECT current_date, AGE (timestamp ‘2001-10-10’);
Output:
Explanation: In the above example, we have considered the age of the person is 10-10-2001. Also, we have subtracted this age from the current date. After subtracting the age of the person are 18 years, 7 months, and 23 days. Basically age function is using the current system time to calculate the age. If we need to calculate age for different times then we need to pass two-argument with age function. PostgreSQL age function will perform the two different calculations, it depends on which parameter we have passed with age function. We are providing two date timestamps and we have also provided a current timestamp in the first parameter.
Age function in PostgreSQL will return the result in the following format are as follows:
XXXX(Year): xx(Month) -xx (Day): It is defined as the first result is the year, the second result is the month and the third result is the day.
xx (Month): xx (Day): It is defined as the first result is the month, the second result is the day.
xx (Day): It will return only days as result using age function.
The return type of age function in PostgreSQL is an interval. Age function in PostgreSQL is used in PostgreSQL versions of 8.4 to 12. We using age function in business applications where we have calculated the age of persons, year of service of the employee, and where we have to calculate the number of years, month, and days. Age function is basically used in web applications where we need to calculate the age of students or employees. Age function calculates the result from the midnight of the day. It will update the next day from midnight. Suppose we need tp calculate the difference between the current date and yesterday’s date using age function. It will update the age from midnight (12:00 clock). Age function will calculate the day in 24-hour format.
Below example shows that age function will return the result from the midnight as 12:00 clock:
Code:
SELECT current_date, AGE (timestamp '2020-06-02');
SELECT current_date, AGE (timestamp '2020-06-01');
Output:
Explanation: In the above first example we have used todays date with current date function then age function will return the result as zero days. In the second example, we have used yesterday’s date after using yesterday’s date with the current date it will return the result as one day.
Examples to Implement PostgreSQL age()
Below are the examples mentioned:
Example #1. Use two timestamp value with age function
In the below example, we have passed two date values with age function. In the first timestamp, we have passing timestamp value as “2020-01-01” and in second timestamp we have passing timestamp value as “2001-01-01”.
Code:
SELECT AGE (timestamp '2020-01-01', timestamp '2001-01-01');
Output:
Example #2. Use two timestamp value with age function
(Use first date is less than the second date)
In the below example we have passing two date values with age function. In the first timestamp, we have passing timestamp value as “2001-01-01” and in second timestamp we have passing timestamp value as “2020-01-01”.
Code:
SELECT AGE (timestamp '2001-01-01', timestamp '2020-01-01');
Output:
Example #3. Use two current date value with age function
In the below example, we have used the current date in the first parameter and the second parameter we have used data as “2001-01-01”.
Code:
two current date
SELECT AGE (timestamp '2001-01-01');
SELECT current_date, AGE (timestamp '2001-01-01');
Output:
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