CREATE TABLE t1 (

  a TIMESTAMP(6) DEFAULT NOW(),

  b TIMESTAMP(6) DEFAULT NOW(0),

  c TIMESTAMP(6) DEFAULT (NOW() + INTERVAL 1 DAY)

);

SHOW CREATE TABLE t1;

first column: NOW() becomes NOW(6), second column: NOW(0) becomes NOW(6), third column: NOW() becomes NOW(0). Same with CURRENT_TIMESTAMP, same in AS OF.

Suggested solution: implement sql standard behavior, where CURRENT_TIMESTAMP() means CURRENT_TIMESTAMP(6). According to SQL:2016, Part 2, Section 6.1 <data type>, Syntax Rules:

36) If <time precision> is not specified, then 0 (zero) is implicit. If <timestamp precision> is not specified, then 6 is implicit.

Perhaps we'll do an old_mode setting of DEFAULT_NOW_0 to let users to revert to the old behavior temporarily.