oracle query column name

In Oracle database, we often need to query the column names of tables and their data types for further analysis and manipulation of data. Below I will introduce several methods to query the column names and data types of Oracle tables.

1. DESC command
   The DESC command is the simplest and most direct method. It can directly query the structural information of the table and list each column name of the table and its data type.

For example, the following statement can query the column name and data type of a table named "employees":

DESC employees;

The output results will be displayed Column name, data type, whether it is empty, default value and other information.

2. USER_TAB_COLUMNS table
   USER_TAB_COLUMNS table can provide more detailed table column information, including data type, column comments, column width, etc. Additionally, it can query the view's column names and data types.

For example, the following statement can query the column name and data type of a table named "employees":

SELECT column_name, data_type
FROM user_tab_columns
WHERE table_name = 'employees';

The output results will display the name and corresponding data type of each column in the table.

3. ALL_TAB_COLUMNS table
   The ALL_TAB_COLUMNS table can query the column names and data types of all accessible objects (tables, views, etc.), including system tables, objects created by other users, etc. It also provides more column information such as comments, default values, null flags, etc.

For example, the following statement can query the column names and data types of all tables or views named "employees":

SELECT owner, table_name, column_name, data_type, nullable, data_default
FROM all_tab_columns
WHERE table_name LIKE 'employees';

The output results will display the name, data type, whether it is empty, default value and other information of each column in each table or view.

4. COLS table
   The COLS table is a system table used to query column information of the table. It provides table name, column name, data type, default value and other information.

For example, the following statement can query the column name and data type of a table named "employees":

SELECT column_name, data_type, data_default
FROM cols
WHERE table_name = 'employees';

The output results will display the name, data type, default value and other information of each column in the table.

Summary
The above are several methods for querying Oracle table column names and data types. Each method has its advantages and disadvantages. Depending on the actual needs and the amount of data to be queried, choosing an appropriate method can improve query efficiency and accuracy.

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