Although the DESC command can view the structure of the table, sometimes it is desirable to enter the structure of the table into a table or into EXCEL. Using the DESC command is a bit tedious. In fact, a SQL statement can be.

Query the table structure of the table you can see:

SELECT T1.TABLE_NAME,
       T1.COLUMN_NAME,
       T1.DATA_TYPE || '(' || T1.DATA_LENGTH || ')',
       T2.COMMENTS
  FROM USER_TAB_COLS T1, USER_COL_COMMENTS T2
 WHERE T1.TABLE_NAME = T2.TABLE_NAME
   AND T1.COLUMN_NAME = T2.COLUMN_NAME
   AND T1.TABLE_NAME = 'EMP';

If it is DBA, it is possible to query all table structures through ALL_ and DBA_.

The writing method of SQL92, but I don't know how to add restrictions. It seems that USING can't be used. Of course, you can remove USING and replace it with ON

SELECT TABLE_NAME,
       COLUMN_NAME,
       T1.DATA_TYPE || '(' || T1.DATA_LENGTH || ')',
       T2.COMMENTS
  FROM USER_TAB_COLS T1 INNER JOIN USER_COL_COMMENTS T2
  USING(table_name,COLUMN_name);

Note that if some fields are not commented, they cannot be displayed. Change it like this:
SELECT t.table_name,
       t.colUMN_NAME,
       t.DATA_TYPE || '(' || t.DATA_LENGTH || ')',
       t1.COMMENTS
  FROM User_Tab_Cols t , User_Col_Comments t1
 WHERE t.table_name = t1.table_name
    AND t.column_name = t1.column_name(+);
Just add an outer join.