Mysql does not allow you to use now() as the default value of a column.
From their docs:
"The DEFAULT clause specifies a default value for a column. With one
exception, the default value must be a constant; it cannot be a function
or an expression. This means, for example, that you cannot set the
default for a date column to be the value of a function such as NOW() or
CURRENT_DATE. The exception is that you can specify CURRENT_TIMESTAMP as
the default for a TIMESTAMP column. See Section 11.3.1.1, "TIMESTAMP
Properties as of MySQL 4.1". "
So they work around this major shortcoming by giving people the
CURRENT_TIMESTAMP constant for the timestamp column so at least the
people wanting an automatic timestamps are happy. Basically they add
just enough support to do the most common thing.
Postgres, allows all of the functions in a create table statement. This
is legit in postgres:
create table test_tab (data varchar(20), timestamp timestamp default
now() - interval '32.56 minutes');
right mysql implementation of defaults is a complete disaster, a big
contributing factor as to why mysql tends to favor application code.
In contrast, pg follows the principle of least suprise, becuase the
internal structures are open and highly generic. the syntax is
standardized and regular (as much as with possible somehow) wherever
possible with carefully thought out exceptions.
mysql syntax, otoh, is hacky and full of special cases. each basic
sql command is highly nuanced and full of legacy workarounds to
limitations of previous versions of mysql. some of the specific
commands (insert, especially) are quite powerful but the whole adds up
to less than the sum of its parts somehow.
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