Mysql – “Incorrect string value” while migrating from MSSQL to MySQL with Workbench

Well, since you have data currently stored in SQL Server, and it's already in an NVARCHAR column, then either it's an NVARCHAR <= 4000 (in which case you can't lose any data, and should just change all instances of NVARCHAR(8000) to NVARCHAR(4000)), or it's an NVARCHAR(MAX) column, in which case you change all instances of NVARCHAR(8000) to NVARCHAR(MAX). Or just leave out those CASTs - do you really need them?

As an aside, you should probably change as NTEXT to as NVARCHAR(MAX) as well.

'2013-08-25T17:00:00+00:00'

This is a valid iso-8601 datetime value, but it is not a valid MySQL datetime literal. On that point, the developer is incorrect.

The documentation explains what ALLOW_INVALID_DATES does:

Check only that the month is in the range from 1 to 12 and the day is in the range from 1 to 31.

In other words, 2013-02-31 would be a permissible date if allow_invalid_dates is set. This option does not do anything when the date or datetime isn't even in a valid format for MySQL.

The +00:00 is the timezone offset from UTC. In this case, the time expressed is in UTC, so the offset is zero hours, zero minutes.

Your workaround would be to remove the STRICT_TRANS_TABLES from the sql_mode that is a default in the config file created during the MySQL 5.6 installation process... you need to carefully consider the implications of changing this, but it does allow the data to go in.

mysql> select @@sql_mode;
+--------------------------------------------+
| @@sql_mode                                 |
+--------------------------------------------+
| STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |
+--------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into datetimetest(dt) values ('2013-08-26T12:00:00+00:00');
ERROR 1292 (22007): Incorrect datetime value: '2013-08-26T12:00:00+00:00' for column 'dt' at row 1

-- remove STRICT_TRANS_TABLES -- note that executing this only removes it for your
-- current session -- it does not make a server-wide config change

mysql> set @@sql_mode='no_engine_substitution';
Query OK, 0 rows affected (0.00 sec)

mysql> select @@sql_mode;
+------------------------+
| @@sql_mode             |
+------------------------+
| NO_ENGINE_SUBSTITUTION |
+------------------------+
1 row in set (0.00 sec)

-- now MySQL will accept the invalid value, with a warning

mysql> insert into datetimetest(dt) values ('2013-08-26T12:00:00+00:00');
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+-----------------------------------------+
| Level   | Code | Message                                 |
+---------+------+-----------------------------------------+
| Warning | 1265 | Data truncated for column 'dt' at row 1 |
+---------+------+-----------------------------------------+
1 row in set (0.00 sec)

-- the value did get inserted, but the time zone information was lost:

mysql> select * from datetimetest;
+----+---------------------+
| id | dt                  |
+----+---------------------+
|  1 | 2013-08-26 12:00:00 |
+----+---------------------+
1 row in set (0.00 sec)