STR_TO_DATE giving an error instead of null - mysql

Question

I am taking data from a csv file and throwing it all into a tempory table, so everything is in string format.
So even date fields are in string format, so I need to convert date from string to a date. All dates are in this format 28/02/2013
I used STR_TO_DATE for this, but I am having a problem.
Here is a snippet of my code.
INSERT INTO `invoice` (`DueDate`)
SELECT
STR_TO_DATE('','%d/%m/%Y')
FROM `upload_invoice`
There are of course more fields than this, but I am concentrating on the field that doesn't work.
Using this command if a date is invalid it should put in a null, but instead of a null being put in, it generates an error instead.
#1411 - Incorrect datetime value: '' for function str_to_date
I understand what the error means. It means it is getting an empty field instead of a properly formatted date, but after reading the documentation it should not be throwing an error, but it should inserting a null.
However if I use the SELECT statement without the INSERT it works.
I could do the following line which actually works to a point
IF(`DueDate`!='',STR_TO_DATE(`DueDate`,'%d/%m/%Y'),null) as `DueDate`
So STR_TO_DATE doesn't run if the field is empty. Now this works, but it can't check for a date which is not valid eg if a date was ASDFADFAS.
So then I tried
IF(TO_DAY(STR_TO_DATE(`DueDate`,'%d/%m/%Y') IS NOT NULL),STR_TO_DATE(`DueDate`,'%d/%m/%Y'),null) as `DueDate`
But this still gives the #1411 error on the if statement.
So my question is why isn't STR_TO_DATE not returning NULL on an incorrect date? I should not be getting the #1411 error.
This is not an exact duplicate of the other question. Also there was not a satisfactory answer. I solved this a while and I have added my solution, which is actually a better solution that was given in the other post, so I think because of my better answer this should stay.

Answer 1

An option you can try:
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.19 |
+-----------+
1 row in set (0.00 sec)
mysql> DROP TABLE IF EXISTS `upload_invoice`, `invoice`;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE IF NOT EXISTS `invoice` (
-> `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> `DueDate` DATE
-> );
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE IF NOT EXISTS `upload_invoice` (
-> `DueDate` VARCHAR(10)
-> );
Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO `upload_invoice`
-> (`DueDate`)
-> VALUES
-> ('ASDFADFAS'), (NULL), (''),
-> ('28/02/2001'), ('30/02/2001');
Query OK, 5 rows affected (0.01 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> INSERT INTO `invoice`
-> SELECT
-> NULL,
-> IF(`DueDate` REGEXP '[[:digit:]]{2}/[[:digit:]]{2}/[[:digit:]]{4}' AND
-> UNIX_TIMESTAMP(
-> STR_TO_DATE(`DueDate`, '%d/%m/%Y')
-> ) > 0,
-> STR_TO_DATE(`DueDate`, '%d/%m/%Y'),
-> NULL)
-> FROM `upload_invoice`;
Query OK, 5 rows affected (0.00 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> SELECT `id`, `DueDate`
-> FROM `invoice`;
+----+------------+
| id | DueDate |
+----+------------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | 2001-02-28 |
| 5 | NULL |
+----+------------+
5 rows in set (0.00 sec)
See db-fiddle.

Answer 2

I forgot I posted this question, but I solved this problem a while ago like this
IF(`{$date}`!='',STR_TO_DATE(`{$date}`,'%d/%m/%Y'),null) as `{$date}`
So because the line is long and confusing I made a function like this
protected function strDate($date){
return "IF(`{$date}`!='',STR_TO_DATE(`{$date}`,'%d/%m/%Y'),null) as `{$date}`";
}
INSERT INTO `invoice` (`DueDate`)
SELECT
{$this->strDate('DueDate')}
FROM `upload_invoice`
I really forgot I posted this question. It seems like an eternity away, but this is how I solved the issue.