Add, delete, modify, and query tables in the basic Oracle tutorial

Oracle table management-how to create a table
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Create a table
Student table
SQL> create table student (
Xh number (4), -- Student ID
Xm varchar2 (20), --- name
Sex char (2), --- gender
Birthday date, --- date of birth
Sal number (7, 2), ---- Scholarship
);
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Table Modification
Add a field
SQL> alter table student add (classid number (2 ));
Modify the length of a field
SQL> alter table student modify (xm varchar2 (30 ));
Delete A Field
SQL> alter table student drop column sal;
Modify Table Name
SQL> rename student to stu
Delete table
SQL> drop table student;

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Add data
Default date format in Oracle 'dd-MON-YY 'DD Day (day) mon Is month

Yy is a two-digit year.
Change the default format of the date:
Alter seesion set nls_date_format = 'yyyy-mm-dd'

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When you insert null data in the database, you want

Check this data
Incorrect: select * from student where birthday = '';
Correct: select * from student where birthday is null;
This is different from other databases in Oracle.
Select * from student where birthday is not null;