How to use the DATEDIFF function in MySQL to calculate the number of days difference between two dates

How to use the DATEDIFF function in MySQL to calculate the number of days difference between two dates

In the MySQL database, the DATEDIFF function can easily calculate the number of days difference between two dates. This function accepts two dates as parameters and returns the difference in days between them.

The syntax for using the DATEDIFF function is as follows:

DATEDIFF(date1, date2)

Among them, date1 and date2 are the two date parameters to be compared. These two parameters can be date type column names, date values, or date expressions.

Here are some common usage examples:

1. Calculate the difference in days between two dates:

SELECT DATEDIFF('2021-12-31', '2021-01-01') AS day_diff;

In this example, we pass DATEDIFF The function calculates the number of days between December 31, 2021 and January 1, 2021. The result will return 365, indicating that the difference between the two dates is 365 days.

2. Use date type column names to calculate the difference in days:

Suppose there is a table orders, which contains two date fields: the creation time and completion time of the order. We want to calculate the processing time for each order.

SELECT order_id, DATEDIFF(complete_date, create_date) AS process_duration FROM orders;

In this example, we use the DATEDIFF function to calculate the number of days between the completion date and the creation date of the order, and name the result process_duration. Through this query, we can get the processing time of each order.

3. Use date expressions to calculate the difference in days:

SELECT DATEDIFF(NOW(), '2021-01-01') AS days_since_new_year;

In this example, we use the date expression NOW() to get the current date and compare it with 2021 The comparison was made on January 1, and the difference in days to New Year was calculated.

It should be noted that the result returned by the DATEDIFF function is an integer, representing the difference in days between the two dates. If one of the two dates is empty, the function returns NULL.

To summarize, the DATEDIFF function is a commonly used function in MySQL for calculating the number of days between dates. Whether it is calculating the interval between two specific dates, or calculating the interval between a certain date and the current date, this function can help us perform calculations quickly.

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