梦想有多远

关于not_null

A column in a table can be specified not null. It’s not possible to insert a null in such a column. The default is null. So, in the following create table statement, a null can be inserted into the column named c.

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创建一个登陆信息登记表
create table login_log
(
session_id int not null,
login_on_time date,
login_off_time date,
user_in_db varchar2(30),
machine varchar2(20),
run_program varchar2(20)
);

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 [youku cg00XMTI0OTEwMA==]

[youku XNDI0Mjk2]

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