How do I list all the columns in a table?

Question

For MySQL, use:

DESCRIBE name_of_table;

This also works for Oracle as long as you are using SQL*Plus, or Oracle's SQL Developer.

For Oracle (PL/SQL)

SELECT column_name
FROM user_tab_cols
WHERE table_name = 'myTableName'

For MySQL

SHOW COLUMNS FROM table_name

For MS SQL Server:

select * from information_schema.columns where table_name = 'tableName'

(5 years laters, for the Honor of PostgreSQL, the most advanced DDBB of the Kingdom)

In PostgreSQL:

\d table_name

Or, using SQL:

select column_name, data_type, character_maximum_length
    from INFORMATION_SCHEMA.COLUMNS 
    where table_name = 'table_name';

I know it's late but I use this command for Oracle:

select column_name,data_type,data_length from all_tab_columns where TABLE_NAME = 'xxxx' AND OWNER ='xxxxxxxxxx'

SQL Server

SELECT 
    c.name 
FROM
    sys.objects o
INNER JOIN
    sys.columns c
ON
    c.object_id = o.object_id
AND o.name = 'Table_Name'

or

SELECT 
    COLUMN_NAME 
FROM 
    INFORMATION_SCHEMA.COLUMNS
WHERE 
    TABLE_NAME  = 'Table_Name'

The second way is an ANSI standard and therefore should work on all ANSI compliant databases.