python cx_Oracle无法更新空时间戳值

Question

I'm trying to update TIMESTAMP column in table with None value in python code.

It worked perfectly when using insert statement with null value.

But when using update statement, it doesn't work!!

following is test code for your understanding.

(The reason why I'm updating 'None' value is that the new value is from the other database, and I want to update the value with the new one, and some of the values are NULL.)

:1 is '20160418154000' type string in python code but when it is 'None' value it raise exception.

INSERT INTO TEST_TABLE (ARR_TIME) VALUES(TO_TIMESTAMP(:1, 'YYYYMMDDHH24MISS'))

it works well!!

UPDATE TEST_TABLE SET ARR_TIME = TO_TIMESTAMP(:1, 'YYYYMMDDHH24MISS')

it doesn't work!!

error message : ORA-00932: inconsistent datatypes: expected - got NUMBER

I think cx_Oracle recognize the None value in python as number (0??) and it cannot be converted to 'YYYYMMDDHH24MISS' string type.

Is there way to update NULL value in TIMESTAMP column?

Answer 1

Yes, there is. Unless you specify otherwise, nulls are bound as type string. You can override this, though, using the following code:

cursor.setinputsizes(cx_Oracle.TIMESTAMP)

See here for documentation:

http://cx-oracle.readthedocs.org/en/latest/cursor.html#Cursor.setinputsizes

NOTE: you could have also solved this by using this code instead:

update test_table set arr_time = :1

There is no need to convert the data using to_timestamp() as cx_Oracle can bind timestamp values directly (use datetime.datetime) and if you bind None Oracle will implicitly convert for you.