How to view the number of fields in a table in the Oracle database

To query the total number of fields in a table in Oracle, use an SQL statement or Copy codeThe Code is as follows: select count (column_name) from user_tab_columns where table_name = 't_ B _AUDITOR'

The number of fields in the specified table can be found.
The following is a rough view:
Select tname, count (*) from col group by tname;
Copy codeThe Code is as follows: 64 T_A_BOOKSTAGEINFO 4
65 T_ B _AUDITOR 14
66 T_ B _BOOKMANAGEMENT 13
67 T_ B _BOOKSTATUSCONFIG 5
68 T_ B _CODETREEINFO 8
69 T_ B _FILTERWORD 11
70 T_ B _ISBNWHITELIST 11
71 T_ B _MODEL 10
72 T_ B _NOTICE 15
73 T_ B _NOTICEACCEPT 11
74 T_ B _OPERLOG 10
75 T_ B _ORGANIZATIONINFO 18
76 T_ B _PREFIXINFO 15
77 T_ B _PUBLISHINFO 30
78 T_ B _ROLE 8
79 T_ B _ROLEMODEL 6
80 T_ B _SAMPLEBOOKINFO 89
81 T_ B _USER 26
82 T_ B _USERANDROLE 6
83 T_ B _USERLOGIN 8
84 T_ B _USERMODEL 6

Now I think of mysql:
Directly use functions to solve the problem:
Copy codeThe Code is as follows: mysql> desc test;
+ --------- + ------------- + ------ + ----- + --------- + ---------------- +
| Field | Type | Null | Key | Default | Extra |
+ --------- + ------------- + ------ + ----- + --------- + ---------------- +
| Id | int (11) | NO | PRI | NULL | auto_increment |
| Name | varchar (10) | YES | NULL |
| Address | varchar (30) | YES | NULL |
+ --------- + ------------- + ------ + ----- + --------- + ---------------- +
3 rows in set (0.01 sec)
Mysql> select found_rows ();
+ -------------- +
| Found_rows () |
+ -------------- +
| 3 |
+ -------------- +
1 row in set (0.01 sec)

There is also the use of system tables:
Copy codeThe Code is as follows: mysql> use information_schema
Database changed
Mysql> select count (*) from columns where table_name = "test ";
+ ---------- +
| Count (*) |
+ ---------- +
| 3 |
+ ---------- +
1 row in set (0.00 sec)

In mysql, you want to know the number of databases in the database:
Copy codeThe Code is as follows: mysql> select * from schemata;
+ -------------- + -------------------- + ------------------------------ + ---------------------- + ---------- +
| CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL _PATH |
+ -------------- + -------------------- + ------------------------------ + ---------------------- + ---------- +
| NULL | information_schema | utf8 | utf8_general_ci | NULL |
| NULL | mysql | utf8 | utf8_general_ci | NULL |
| NULL | test | utf8 | utf8_general_ci | NULL |
+ -------------- + -------------------- + ------------------------------ + ---------------------- + ---------- +
3 rows in set (0.00 sec)

The number of tables in the mysql database:
Copy codeThe Code is as follows: mysql> select table_schema, count (*) from tables group by table_schema;
+ -------------------- + ---------- +
| Table_schema | count (*) |
+ -------------------- + ---------- +
| Information_schema | 17 |
| Mysql | 17 |
| Test | 6 |
+ -------------------- + ---------- +
3 rows in set (0.00 sec)

In fact, most databases and tables in the system table information_schema will have records. So study this table.