SQL Reference

Example

USE myDatabase;
DESC myTable;

Output

+---------+-------------+------+-----+---------+----------------+
| Field   | Type        | Null | Key | Default | Extra          |
+---------+-------------+------+-----+---------+----------------+
| id      | int(11)     | NO   | PRI | NULL    | auto_increment |
| name    | varchar(45) | YES  |     | NULL    |                |
| age     | int(11)     | YES  |     | NULL    |                |
+---------+-------------+------+-----+---------+----------------+

Explanation

The DESC statement is used in MySQL to describe the structure of a specified table in the database. In this example, DESC myTable; shows the columns (Field), data types (Type), whether NULL values are allowed (Null), the Key status of each column, the Default values, and any Extra information for each column in the myTable within myDatabase.

Example

DESC employees;

Output

name     |  type   | nullable  | default
---------+---------+-----------+-----------
id       | integer | not null  | nextval('employees_id_seq'::regclass)
name     | text    | not null  |
address  | text    | not null  |
email    | text    |           |

Explanation

DESC is a command in PostgreSQL that provides the description of a table. It lists all columns, their data types, whether they can be null, and their default values, if any. In the above example, DESC employees; is providing the description of the employees table.

Example

SELECT * FROM Customers
ORDER BY CustomerID DESC;

Output

+------------+-----------------+-------------+-----------+----------+
| CustomerID | CustomerName    | ContactName | Country   | Phone    |
+------------+-----------------+-------------+-----------+----------+
| 91         | Bon app         | John Smith  | USA       | 12345678 |
| 90         | White Clover    | Mary Johnson| Ireland   | 23456789 |
| 89         | North/South     | James Brown | UK        | 34567891 |
+------------+-----------------+-------------+-----------+----------+

Explanation

The command showcases the use of DESC keyword in SQL which sorts the results in a descending order as per the column mentioned after ORDER BY clause i.e., CustomerID in this scenario. After execution, the Customers table is displayed with records arranged in descending order of CustomerID.

Example

DESC employees;

Output

Name       Null     Type
---------- -------- ------------
EMPLOYEE_ID NOT NULL NUMBER(6)
FIRST_NAME  NULL     VARCHAR2(20)
LAST_NAME   NOT NULL VARCHAR2(25)
EMAIL       NOT NULL VARCHAR2(25)
PHONE_NUMBER NULL    VARCHAR2(20)

Explanation

The DESC command in SQL is used to display the structure of a table. It provides a detailed view of each attribute (column) in the table, including the type of data associated with the attribute and whether the attribute allows null values or not. This example shows the structure of the employees table.

Example

CREATE TABLE  Employees (
    ID INT PRIMARY KEY NOT NULL,
    NAME TEXT NOT NULL,
    AGE INT NOT NULL,
    ADDRESS CHAR(50),
    SALARY REAL );

INSERT INTO Employees (ID, NAME, AGE, ADDRESS, SALARY)
VALUES (1, 'Paul', 32, 'California', 20000.00);

INSERT INTO Employees (ID, NAME, AGE, ADDRESS, SALARY)
VALUES (2, 'Allen', 25, 'Texas', 15000.00);

SELECT * FROM Employees
ORDER BY SALARY DESC;

Output

ID          NAME        AGE         ADDRESS    SALARY
----------  ----------  ----------  --------   --------
1           Paul        32          California 20000.0
2           Allen       25          Texas      15000.0

Explanation

The SQL DESC command is used in the ORDER BY clause to sort the data in descending order. The example demonstrated sorts the column ‘SALARY’ in descending order. In the output, you can see that the employee with the highest salary is listed first.