MySQL Incorrect datetime value: '0000-00-00 00:00:00'

I wasn't able to do this:

UPDATE users SET created = NULL WHERE created = '0000-00-00 00:00:00'

(on MySQL 5.7.13).

I kept getting the Incorrect datetime value: '0000-00-00 00:00:00' error.

Strangely, this worked: SELECT * FROM users WHERE created = '0000-00-00 00:00:00'. I have no idea why the former fails and the latter works... maybe a MySQL bug?

At any case, this UPDATE query worked:

UPDATE users SET created = NULL WHERE CAST(created AS CHAR(20)) = '0000-00-00 00:00:00'

Changing the default value for a column with an ALTER TABLE statement, e.g.

 ALTER TABLE users MODIFY created datetime  NULL DEFAULT '1970-01-02'

... doesn't change any values that are already stored. The "default" value applies to rows that are inserted, and for which a value is not supplied for the column.

---

As to why you are encountering the error, it's likely that the sql_mode setting for your session includes NO_ZERO_DATE.

Reference: http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_no_zero_date

When you did the "import", the SQL statements that did the INSERT into that table were run in a session that allowed for zero dates.

To see the sql_mode setting:

SHOW VARIABLES LIKE 'sql_mode' ;

-or-

SELECT @@sql_mode ;

As far as how to "fix" the current problem, so that the error won't be thrown when you run the ALTER TABLE statement.

Several options:

1) change the sql_mode to allow zero dates, by removing NO_ZERO_DATE and NO_ZERO_IN_DATE. The change can be applied in the my.cnf file, so after a restart of MySQL Server, sql_mode variable will be initialized to the setting in my.cnf.

For a temporary change, we can modify the setting with a single session, without requiring a global change.

-- save current setting of sql_mode
SET @old_sql_mode := @@sql_mode ;

-- derive a new value by removing NO_ZERO_DATE and NO_ZERO_IN_DATE
SET @new_sql_mode := @old_sql_mode ;
SET @new_sql_mode := TRIM(BOTH ',' FROM REPLACE(CONCAT(',',@new_sql_mode,','),',NO_ZERO_DATE,'  ,','));
SET @new_sql_mode := TRIM(BOTH ',' FROM REPLACE(CONCAT(',',@new_sql_mode,','),',NO_ZERO_IN_DATE,',','));
SET @@sql_mode := @new_sql_mode ;

-- perform the operation that errors due to "zero dates"

-- when we are done with required operations, we can revert back
-- to the original sql_mode setting, from the value we saved
SET @@sql_mode := @old_sql_mode ;

2) change the created column to allow NULL values, and update the existing rows to change the zero dates to null values

3) update the existing rows to change the zero dates to a valid date

---

We don't need to run individual statements to update each row. We can update all of the rows in one fell swoop (assuming it's a reasonably sized table. For a larger table, to avoid humongous rollback/undo generation, we can perform the operation in reasonably sized chunks.)

In the question, the AUTO_INCREMENT value shown for the table definition assures us that the number of rows is not excessive.

If we've already changed the created column to allow for NULL values, we can do something like this:

UPDATE  `users` SET `created` = NULL WHERE `created` = '0000-00-00 00:00:00'

Or, we can set those to a valid date, e.g. January 2, 1970

UPDATE  `users` SET `created` = '1970-01-02' WHERE `created` = '0000-00-00 00:00:00'

(Note that a datetime value of midnight Jan 1, 1970 ('1970-01-01 00:00:00') is a "zero date". That will be evaluated to be '0000-00-00 00:00:00'

I got it fixed by doing this before the query

SET SQL_MODE='ALLOW_INVALID_DATES';