> SET start_date=STR_TO_DATE(@date_as_string,'%m/%d/%y');

Dates have 4 digits in your data, right? %y and %Y are different.

gordon/(none)> select str_to_date('11/29/1999', '%m/%d/%y');
+---------------------------------------+
| str_to_date('11/29/1999', '%m/%d/%y') |
+---------------------------------------+
| 2019-11-29 |
+---------------------------------------+
1 row in set, 1 warning (0.00 sec)

gordon/(none)> show warnings;
+---------+------+----------------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------------+
| Warning | 1292 | Truncated incorrect date value: '11/29/1999' |
+---------+------+----------------------------------------------+
1 row in set (0.00 sec)

gordon/(none)> select str_to_date('11/29/1999', '%m/%d/%Y');
+---------------------------------------+
| str_to_date('11/29/1999', '%m/%d/%Y') |
+---------------------------------------+
| 1999-11-29 |
+---------------------------------------+
1 row in set (0.01 sec)


>This gets to examine the data, so I guess the syntax is OK. But I
>still get an error about the date. This time, the error is "Truncated
>incorrect date value: "11/22/1999"

%Y and %y are different.

>instead of trying to load it into @var1? Do the names in the list in
>the LOAD DATA statement have to be provided in the order the
>corresponding columns were created in the table?

I doubt it. That would make listing the names rather pointless.

>If not, I can load
>the data first, and that with the data going into a column of type
>char[10], and then run an UPDATE statement in which the SET start_date
>clause above is invoked. Right?

Yes. But fix your format first.

Gordon L. Burditt