How to Efficiently Populate a MySQL Table with a Date Range?

MySQL date range table filling method

When working with a MySQL database, you often need to generate and populate tables containing date ranges. This task would be very tedious if performed manually. This article introduces an efficient automation method.

Suppose we need to populate a MySQL table named "tablename" containing all dates between January 1, 2011 and December 31, 2011. The table has only one DATE type column called "_date".

We can use MySQL stored procedures to achieve:

<code class="language-sql">DROP PROCEDURE IF EXISTS filldates;
DELIMITER |
CREATE PROCEDURE filldates(dateStart DATE, dateEnd DATE)
BEGIN
  WHILE dateStart <= dateEnd DO
    INSERT INTO tablename (_date) VALUES (dateStart);
    SET dateStart = date_add(dateStart, INTERVAL 1 DAY);
  END WHILE;
END |
DELIMITER ;

CALL filldates('2011-01-01', '2011-12-31');</code>

Here’s how the stored procedure works:

1. We create a stored procedure named "filldates" which accepts two input parameters: dateStart and dateEnd.
2. In the stored procedure, we use a WHILE loop to iterate over the date range.
3. Each iteration, we insert a new row into the tablename table using the current dateStart value.
4. After each iteration, we use the date_add() function to add one day to dateStart.
5. We continue this process until dateStart is greater than or equal to dateEnd.
6. After creating the stored procedure, we execute it using a CALL statement to populate the table.

To avoid inserting duplicate dates, you can use the following modified version:

<code class="language-sql">CREATE PROCEDURE filldates(dateStart DATE, dateEnd DATE)
BEGIN
  WHILE dateStart <= dateEnd DO
    IF NOT EXISTS (SELECT 1 FROM tablename WHERE _date = dateStart) THEN
      INSERT INTO tablename (_date) VALUES (dateStart);
    END IF;
    SET dateStart = date_add(dateStart, INTERVAL 1 DAY);
  END WHILE;
END;</code>

This modification ensures that duplicate dates are not inserted into the table.

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