PostgreSQL LENGTH Function

Summary: in this tutorial, we will show you various PostgreSQL length functions that return the number of characters or the number of bytes of a string.

PostgreSQL LENGTH function

The following illustrates the syntax of the length function:

LENGTH(string);
Code language: SQL (Structured Query Language) (sql)

The length function accepts a string as a parameter. A string can be any of the following data types:

• character or char
• character varying or varchar
• text

The length function returns the number of characters in the string.

PostgreSQL length function examples

See the following example of using the length function:

SELECT
	LENGTH ('PostgreSQL Tutorial'); -- 19
Code language: SQL (Structured Query Language) (sql)

Notice that a string can hold an empty string, which is not a null value.

SELECT
	LENGTH (''); -- 0
Code language: SQL (Structured Query Language) (sql)

It returns zero. However, a string that holds a space character:

SELECT
	LENGTH (' '); -- 1
Code language: SQL (Structured Query Language) (sql)

It returns 1.

If you pass a NULL value to the length function, it returns a NULL value.

SELECT
	LENGTH (NULL); -- NULL
Code language: SQL (Structured Query Language) (sql)

The following query gets the full names of customers in the customer table and uses the length function to get the number of characters in their names.

SELECT
	first_name || ' ' || last_name AS name,
	LENGTH (first_name || ' ' || last_name) len
FROM
	customer
ORDER BY
	len;
Code language: SQL (Structured Query Language) (sql)

Sometimes, you may want to measure the length of a number instead of a string. In this case, you use type cast to convert the number into a string and use the length function as the following example:

SELECT
	LENGTH (CAST(12345 AS TEXT)); --- 5
Code language: SQL (Structured Query Language) (sql)

We often use the length function with other string functions such as replace, substring, etc., to manipulate string more efficiently. The following statement gets the user name and domain from the an email address using substring, strpos, and lengthfunctions.

SELECT
	SUBSTRING (
		'[email protected]',
		1,
		strpos(
			'[email protected]',
			'@'
		) - 1
	) AS user_name,
	SUBSTRING (
		'[email protected]',
		strpos(
			'[email protected]',
			'@'
		) + 1,
		LENGTH (
			'[email protected]'
		)
	) AS domain_name;
Code language: SQL (Structured Query Language) (sql)

Besides the length function, PostgreSQL provides the char_length and character_length functions that provide the same functionality.

Measure strings in bytes and bits

To get the number of bytes in a string, you use the octet_length function as follows:

OCTET_LENGTH(string);
Code language: SQL (Structured Query Language) (sql)

See the following example:

SELECT
	OCTET_LENGTH ('A'); -- 1 byte
Code language: SQL (Structured Query Language) (sql)

It returns 1 byte.

SELECT
	OCTET_LENGTH ('€'); -- 3 bytes
Code language: SQL (Structured Query Language) (sql)

It returns 3 bytes. However, with the length function, it returns just 1.

SELECT
	LENGTH ('€'); -- 1
Code language: SQL (Structured Query Language) (sql)

To measure the number of bits of a string, you use the bit_length function as follows:

BIT_LENGTH(string);
Code language: SQL (Structured Query Language) (sql)

See the following examples of using the bit_length function.

SELECT
	BIT_LENGTH ('A'); -- 8 bits
Code language: SQL (Structured Query Language) (sql)

SELECT
	BIT_LENGTH ('€'); -- 24 bits
Code language: SQL (Structured Query Language) (sql)

In this tutorial, we have shown you how to use length, bit_length, and octet_length functions to return the number of characters, the number of bits, and the number of bytes of a string.