Concatenation Operator

Description:

You can link columns to other columns, arithmetic

expressions, or constant values to create a character 

expression by using the concatenation operator (||).

If you concatenate a null value with a character 

string, the result is a character string.

LAST_NAME || NULL results in LAST_NAME.

Examples: 

SELECT  last_name||job_id AS "Employees"

FROM   employees;

The select statement displays LAST_NAME and 

JOB_ID are concatenated, and given the alias 

Employees. Note that the last name of the 

employee"Abel" and the job code"SA_REP" are 

combined to make a single output Column 

"AbelSA_REP".

SELECT last_name ||': 1 Month salary = '||salary Monthly
FROM   employees;

The select statement displays the last names and 

job codes of all employees. The column has the 

heading Employee Details. Note the spaces between

the single quotation marks in the SELECT 

statement.

The spaces improve the readability of the output.