Understanding Amazon Redshift String Functions: 2 Easy Examples

on Amazon Redshift, Data Warehouse, Data Warehouses, SQL, Tutorials • January 18th, 2022 • Write for Hevo

Redshift String Functions

Companies use various apps, services, and platforms to effectively run their business. Big organizations use Cloud Data Warehouses to store and analyze their data so that they can make use of data-driven business decisions. Amazon Redshift String Functions make it easier for users to query and manipulate data from the Data Warehouse. Amazon Redshift String Functions uses standard SQL commands to access data.

In this article, You will learn about the Amazon Redshift String Functions and how to use these different Amazon Redshift String Functions with their syntax and description, to make it easy for you to understand different Amazon Redshift String Functions. Let’s start with a brief introduction to Amazon Redshift, then we will dive into Amazon Redshift String Functions.

Table of Contents

Introduction to Amazon Redshift

Amazon Redshift Logo
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Amazon Redshift is a Data Warehouse product that is part of the broader Cloud Computing platform Amazon Web Services, with the color red being a reference to Oracle, whose corporate color is red and is referred to as Big Red informally. It’s built on ParAccel’s (later Actian’s) massive parallel processing (MPP) Data Warehouse technology, which can handle large data volumes and Database Migrations.

With tens of thousands of users utilizing it to analyze exabytes of data and run complex Analytical queries, Amazon Redshift is the most widely used Cloud Data Warehouse. You can execute and grow Analytics on all of your data in seconds without having to manage your Data Warehouse infrastructure.

Key Features of Amazon Redshift

A few features of Amazon Redshift are listed below:

  • Massive Parallel Processing: Amazon Redshift runs multiple queries on different clusters and distributes the workload on other processors. The MPP helps in delivering fast querying performance.
  • Backup Services: Amazon Redshift offers excellent backup services of Data Warehouse to multiple locations across the world for better availability of data and prevents any data loss in case of any disaster.
  • End-to-End Encryption: Amazon Redshift offers high-end security to secure data. Users can set up SSL for data transfer and hardware-accelerated AES 256 Encryption for hardware at rest.

To learn more about Amazon Redshift, click here.

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Understanding Amazon Redshift String Functions

Amazon Redshift String Functions Image
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Character strings or expressions that evaluate character strings are processed and manipulated using Amazon Redshift String Functions. When passing a literal value as a string argument to these functions, it must be contained in single quotation marks. The data types CHAR and VARCHAR are supported. In Amazon Redshift String Functions, all offsets are one-based. 

The names, syntax, and explanations of supported Amazon Redshift String Functions are listed below. 

1) ASCII Function

Syntax: ASCII(string)

Description: The ASCII method returns the first character of a string’s ASCII code or Unicode code-point. The function returns 0 if the string is empty. It returns null if the string is null.

2) CHARACTER_LENGTH Function

Syntax: LEN(expression) / LENGTH(expression) / CHAR_LENGTH(expression) /CHARACTER_LENGTH(expression) / TEXTLEN(expression)

Description: The LEN function calculates the number of characters in the input string and returns an integer. The LEN function returns the real number of characters in multi-byte strings, not the number of bytes if the input string is a character string. To hold three four-byte Chinese characters, for example, a VARCHAR(12) column is necessary. For the same string, the LEN function will return 3. Use the OCTET LENGTH function to get the length of a string in bytes.

3) BTRIM Function

Syntax: BTRIM(string [, matching_string ] )

Description: The BTRIM function eliminates the leading and trailing spaces. It also cuts strings by finding characters that match.

4) CHARINDEX Function

Syntax: CHARINDEX( substring, string )/ STRPOS(string, substring )

Description: The CHARINDEX function will return an integer that corresponds to the substring’s location (one-based, not zero-based). Multi-byte characters are counted as single characters because the position is based on the number of characters, not bytes. If the substring is not located within the string, CHARINDEX returns 0.

5) CHR Function

Syntax: CHR(number)

Description: The character that matches the ASCII code point value supplied by the input parameter is returned by the CHR function.

6) CONCAT Function

Syntax: CONCAT ( expression1, expression2 )

Description: The CONCAT function joins two expressions together and returns the result. Use layered CONCAT functions to concatenate more than two expressions. The CONCAT function delivers the same results as the concatenation operator (||) between two expressions.

7) INITCAP Function

Syntax: INITCAP(string)

Description: The VARCHAR string is returned by the INITCAP function. The first letter of each word in a string is capitalized.

8) LEFT Function

Syntax: LEFT ( string, integer )

Description: The specified number of leftmost characters is returned by this function. Multibyte characters are counted as single characters because the number is based on the number of characters, not bytes.

9) RIGHT Function

Syntax: RIGHT ( string, integer )

Description: The provided number of the rightmost characters is returned by this function. Multibyte characters are counted as single characters because the number is based on the number of characters, not bytes.

10) LOWER Function

Syntax: LOWER(string)

Description: Reduces the case of a string. UTF-8 multibyte characters, up to four bytes per character, are supported by LOWER.

11) UPPER Function

Syntax: UPPER(string)

Description: Converts a string from lower to upper case.

12) LPAD Function

Syntax: LPAD (string1, length, [ string2 ])

Description: To make a new string, pad the left side of the string with characters. This function adds characters to the end of a string. The VARCHAR data type is returned by these functions.

13) RPAD Function

Syntax: RPAD (string1, length, [ string2 ])

Description: To make a new string, pad the right side of the string with characters. This function adds characters to the end of a string. The VARCHAR data type is returned by these functions.

14) LTRIM Function

Syntax: LTRIM(string, ‘trim_chars’)

Description: The LTRIM function cuts the first characters of a string to a specified length. LTRIM returns the same data type as the input string as a character string (CHAR or VARCHAR).

15) RTRIM Function

Syntax: RTRIM(string, ‘trim_chars’)

Description: The RTRIM function trims the end of a string by a specified number of characters. The string argument is replaced with a string of the same data type

16) QUOTE_IDENT Function

Syntax: QUOTE_IDENT(string)

Description: The QUOTE_IDENT function returns a double-quoted string that can be used as an identifier in a SQL statement. Any inserted double quotation marks are appropriately doubled.

When the string contains non-identifier characters or would otherwise be folded to lowercase, QUOTE IDENT adds double quotation marks only where necessary to establish a valid identifier. Use QUOTE LITERAL to always return a single-quoted string.

17) QUOTE_LITERAL Function

Syntax: QUOTE_LITERAL(string)

Description: The QUOTE_LITERAL function converts a string into a quoted string that may be used as a string literal in a SQL statement. If the input parameter is an integer, it is converted to a string via QUOTE_LITERAL. Any embedded single quotation marks and backslashes are appropriately doubled.

18) POSITION Function

Syntax: POSITION(substring IN string )

Description: The POSITION function returns a number that represents the substring’s position (one-based, not zero-based). Multi-byte characters are counted as single characters because the position is based on the number of characters, not bytes.

19) REPEAT Function

Syntax: REPEAT(string, integer)/ REPLICATE(string, integer)

Description: The number of times a string is repeated is provided. REPEAT interprets the input parameter as a string if it is numeric.

20) REPLACE Function

Syntax: REPLACE(string1, old_chars, new_chars)

Description: Replaces all instances of a set of characters in a string with other characters supplied. TRANSLATE and REGEXP REPLACE are similar functions, but TRANSLATE does many single-character substitutions and REGEXP REPLACE searches a string for a regular expression pattern, whereas REPLACE replaces an entire string with another string.

21) REVERSE Function

Syntax: REVERSE ( expression )

Description: The REVERSE function takes a string and reverses the order of the characters. Reverse(‘abcde’), for example, returns “edcba”. This Amazon Redshift String Function works on numeric and date data types as well as character data types; nevertheless, it is most useful for character strings in most circumstances.

22) SPLIT_PART Function

Syntax: SPLIT_PART(string, delimiter, part)

Description: Splits a text at the delimiter supplied and returns the part at the specified location.

23) SUBSTRING Function

Syntax: SUBSTRING(string, start_position, number_characters ) / SUBSTRING(string FROM start_position [ FOR number_characters ] )

Description: Returns a subset of a text based on the start position specified. If the entry is a character string, the start position and number of extracted characters are determined by characters rather than bytes, hence multi-byte characters are counted as single characters.

The start position and extracted substring are based on bytes if the input is a binary expression. A negative length cannot be specified, although a negative starting position can.

Using Amazon Redshift String Functions

Usage of every Amazon Redshift String Functions is different from each other. Here are a few examples of Amazon Redshift String Functions listed below:

Using SUBSTRING Function

The example below returns a four-character string that starts with the sixth character.

select substring('caterpillar',6,4);
substring
-----------
pill
(1 row)

Using LENGTH Function

The number of bytes and characters in the string français are returned in the following example.

select octet_length('français'), 
len('français');

octet_length  | len
--------------+-----
           9  |   8

Conclusion

In this article, you learnt about Amazon Redshift String Functions and their different functions that are widely used in querying and manipulating data. You also read about a few examples of Amazon Redshift String Functions. All these Amazon Redshift String Functions are very commonly used in processing data. You can just copy-paste the syntax from here to use any Amazon Redshift String Functions according to your need. Almost all the Amazon Redshift String Functions are very easy to use as they are just one to two function commands. 

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