In Oracle, the LOWER() function returns its argument with all letters in lowercase.

Syntax

The syntax goes like this:

LOWER(char)

Where char can be of any of the data types CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. 

Example

Here’s a simple example to demonstrate:

SELECT LOWER('NEW ZEALAND')
FROM DUAL;

Result:

   LOWER('NEWZEALAND') 
______________________ 
new zealand           

The same applies when the argument uses mixed case:

SELECT LOWER('New Zealand')
FROM DUAL;

Result:

   LOWER('NEWZEALAND') 
______________________ 
new zealand           

And if the argument is already lowercase, then the result is the same as the input:

SELECT LOWER('new zealand')
FROM DUAL;

Result:

   LOWER('NEWZEALAND') 
______________________ 
new zealand           

Null Values

Passing null returns null:

SET NULL 'null';

SELECT LOWER(null)
FROM DUAL;

Result:

   LOWER(NULL) 
______________ 
null          

By default, SQLcl and SQL*Plus return a blank space whenever null occurs as a result of a SQL SELECT statement.

However, you can use SET NULL to specify a different string to be returned. Here I specified that the string null should be returned.

Incorrect Argument Count

Calling LOWER() without passing any arguments returns an error:

SELECT LOWER()
FROM DUAL;

Result:

Error starting at line : 1 in command -
SELECT LOWER()
FROM DUAL
Error at Command Line : 1 Column : 8
Error report -
SQL Error: ORA-00909: invalid number of arguments
00909. 00000 -  "invalid number of arguments"
*Cause:    
*Action:

And passing the wrong number of arguments results in an error:

SELECT LOWER('New', 'Zealand')
FROM DUAL;

Result:

Error starting at line : 1 in command -
SELECT LOWER('New', 'Zealand')
FROM DUAL
Error at Command Line : 1 Column : 8
Error report -
SQL Error: ORA-00909: invalid number of arguments
00909. 00000 -  "invalid number of arguments"
*Cause:    
*Action: