How to query field name in oracle

Oracle is a very popular relational database management system, which is widely used in enterprise application systems. When using Oracle for data query, we often need to query the name of a field in the table. This article will introduce several methods of querying field names in Oracle.

1. Query table structure

We can use Oracle's DESC command to query the table structure. The syntax of this command is as follows:

DESC table_name;

where table_name is the name of the table whose structure you want to query. After executing this command, Oracle will return table structure information, including column names, data types, column lengths, etc.

For example, if we want to query all column names and their data types in the EMPLOYEES table, we can use the following command:

DESC employees;

After executing the above command, Oracle The following information will be returned:

Name Null? Type

---

EMPLOYEE_ID NOT NULL NUMBER(6)
FIRST_NAME VARCHAR2(20)
LAST_NAME NOT NULL VARCHAR2(25)
EMAIL NOT NULL VARCHAR2(25)
PHONE_NUMBER VARCHAR2(20)
HIRE_DATE NOT NULL DATE
JOB_ID NOT NULL VARCHAR2(10)
SALARY NUMBER(8,2)
COMMISSION_PCT NUMBER( 2,2)
MANAGER_ID NUMBER(6)
DEPARTMENT_ID NUMBER(4)

As can be seen from the above results, the EMPLOYEES table has 11 columns, namely EMPLOYEE_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, JOB_ID, SALARY, COMMISSION_PCT, MANAGER_ID and DEPARTMENT_ID.

2. Query Data Dictionary

Oracle database comes with a large number of data dictionaries, including information about tables, views, indexes, users, etc. We can get the information we need by querying these data dictionaries. When querying field names, we usually need to use the USER_TAB_COLUMNS data dictionary table, which records the column information of all tables of the current user.

The following is the SQL statement to query all fields in all tables:

SELECT TABLE_NAME, COLUMN_NAME
FROM USER_TAB_COLUMNS;

After executing this statement, Oracle will return the current user All field names in all tables owned.

3. Using metadata query statements

Oracle database provides some metadata query statements, which can be used to query system metadata information. One of the commonly used metadata query statements is ALL_TAB_COLUMNS, which can query all column information in all tables and views.

The following is the SQL statement to query all fields in all tables and views:

SELECT TABLE_NAME, COLUMN_NAME
FROM ALL_TAB_COLUMNS;

After executing this statement, Oracle will return All field names in all tables and views.

4. Using the SQL Developer tool

Oracle provides a very useful tool - SQL Developer, which can be used to connect to the Oracle database and perform various operations. , including the field names in the query table. Querying the field names of a table in SQL Developer is very simple. You only need to right-click the table you want to query and select "Quick DDL" in the pop-up menu. The CREATE TABLE statement will pop up, including information about all fields in the table.

To sum up, there are many ways to query the field names of tables in Oracle, including using the DESC command to query the table structure, querying the data dictionary, using metadata query statements, and using the SQL Developer tool. In practical applications, we can choose the most appropriate method to query field names according to specific circumstances to improve work efficiency and accuracy.

The above is the detailed content of How to query field name in oracle. For more information, please follow other related articles on the PHP Chinese website!