04-functions-and-grouping: Contains errors

[chernbo]

The content in 04-current-date.sql under 04-functions-and-grouping will report an error.

INSERT INTO test
VALUES(CURRENT_DATE() + 1, NULL, NULL);

When a date is converted to the numeric format 20260531 and incremented by 1, it becomes 20260532, which is not a valid date and causes an error.

Recommended Fixes (DATE_ADD / DATE_SUB ):

INSERT INTO test
VALUES(DATE_ADD(CURRENT_DATE(), INTERVAL 1 DAY), NULL, NULL);