Query Date and Time

Query date and time help to analyze trends, forecast future events, and make informed decisions based on historical data. For example, a retailer might analyze sales data by date to identify seasonal trends and plan promotions accordingly.

Also, as a data professional, you may need to query the date and time to update a record to reflect a change in an event or to retrieve all records from a database within a specific date range.

Let’s see how it works.

To query date and time data, you can use the following commands:

• To retrieve the current date:

SELECT CURRENT_DATE;

• To retrieve the current time:

SELECT CURRENT_TIME;

• To retrieve the current date and time:

SELECT CURRENT_TIMESTAMP;

• To filter data based on a specific date or time range:

SELECT *
FROM orders
WHERE order_date >= '2022-01-01' AND order_date <= '2022-03-31';

SELECT *
FROM orders
WHERE order_date BETWEEN '2022-01-01' AND '2022-03-31';

The examples above use the WHERE clause to specify the range you want to retrieve data. You can choose to use the BETWEEN or the comparison operators.

• Group sales data by month:

SELECT MONTH(date_column) as month, SUM(sales_amount) as total_sales
FROM sales_table
GROUP BY MONTH(date_column);

This query will group the sales data in sales_table by month and calculate the total sales amount for each month.

• Retrieve data for the current week:

SELECT *
FROM table_name
WHERE WEEK(transaction_date) = WEEK(CURRENT_DATE)
AND YEAR(transaction_date) = YEAR(CURRENT_DATE);

This is equivalent to

SELECT *
FROM table_name
WHERE DATE_TRUNC(week, transaction_date) = DATE_TRUNC(week, CURRENT_DATE);

The WEEK function returns the week number of a given date. By comparing the week number of the transaction_date to the week number of the CURRENT_DATE, we can retrieve all records within the current week. The YEAR function ensures that the query only retrieves records from the current year. If you don’t include this condition, the query will also retrieve records from the same week in previous years.

• Calculate the average time spent on a task:

SELECT task_name, AVG(TIMESTAMPDIFF(SECOND, start_time, end_time)) as avg_time
FROM task_table
GROUP BY task_name;

This query will calculate the average time spent on each task in “task_table” by subtracting the “start_time” from the “end_time” and calculating the average in seconds using the AVG and TIMESTAMPDIFF functions.