ORACLE Column Alias
ORACLE
An Oracle column alias assigns a temporary name to a column during the result set of an SQL query.
Oracle Column Alias
➔ Column aliases make the output more readable.
➔ This alias exists only for the duration of the execution of that particular query.
➔ The AS keyword is optional if there are no spaces in the alias name.
➔ If there are no spaces in the alias name, it is not mandatory to use quotes around the alias name.
➔ If the column alias name contains spaces, special characters, or requires specific case preservation of characters, the column alias name must be enclosed in double quotation marks.
➔ Column aliases are very helpful when using concatinating or calculative expressions and the column headings for those expressions become too long.
Syntax
If the alias name does not contain any spaces, the AS keyword is not required.
/* Oracle column alias */
SELECT column_name AS alias_name
FROM table_name;
Syntax
/* Oracle column alias */
SELECT column_name AS alias_name
FROM table_name;
Syntax
/* Oracle column alias with space */
SELECT column_name AS "alias name"
FROM table_name;
Example
/* Oracle column alias */
SELECT EMPLOYEE_ID AS ID
FROM employees;
Example: column alias in expression
/* Oracle column alias in expression */
SELECT EMPLOYEE_ID AS ID FIRST_NAME || LAST_NAME AS NAME
FROM employees;
Oracle Example 1
select * from employees;
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Oracle Example 2
select * from departments;
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The best way to learn is to implement it yourself after any lesson.
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Create table:
Example
/* Drop table if the table name is already exists */
DROP TABLE IF EXISTS demo_column_alias;
/* Create Table*/
CREATE TABLE demo_column_alias (
employee_id NUMBER(6) PRIMARY KEY,
first_name VARCHAR2(20),
last_name VARCHAR2(20),
salary NUMBER(8, 2),
department_id NUMBER(4)
);
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Insert value:
Example
INSERT INTO demo_column_alias(employee_id, first_name, last_name, salary, department_id)
VALUES (101, 'Neena', 'Kochhar', 17000, 90);
INSERT INTO demo_column_alias (employee_id, first_name, last_name, salary, department_id)
VALUES (102, 'Lex', 'De Haan', 17000, 90);
INSERT INTO demo_column_alias (employee_id, first_name, last_name, salary, department_id)
VALUES (103, 'Alexander', 'Hunold', 9000, 60);
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Check the query results against the data.
Example
SELECT employee_id AS "ID" first_name || last_name AS "FULL NAME"
FROM demo_column_alias;
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If desired, delete the table after finishing the exercise.
Example
/* Drop the table from the schema. */
DROP TABLE demo_column_alias;
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