Finding non-printable characters in MSSQL Finding non-printable characters in MSSQL

String fields in MSSQL accept non-printable characters such as tabs, line breaks, etc. When your application has not prevented this characters from being removed and you want to determine if these characters exist in your field, the UNICODE is your friend to answer this question.

Table of contents:

SQL Server find non printable characters

The UNICODE returns an ASCII integer for the character passed into the function. Here is the most simplistic example to see what it returns:


The character inside is a tab. Running the query above returns: 9, a horizontal tab. Here is a list of non-printable ASCII characters. In my case I care about all characters that are less than 32. 33 is a space, but I can live with trimming them, unless it is important to find leading and trailing spaces.

The UNICODE function accepts a string of more than one printable characters; however, it only returns against the first character. So to get the best result and search every char of our string, I will write a while loop.

DECLARE @position int = 1,
@stringToSearch varchar(255) = 'tab and a
line break'
WHILE @position <= LEN(@stringToSearch)
DECLARE @currentChar char(1) = SUBSTRING(@stringToSearch, @position, 1)
DECLARE @currentAsciiValue int = UNICODE(@currentChar)
IF @currentAsciiValue < 32
SELECT @currentAsciiValue as AsciiValue
, STRING_ESCAPE(@currentChar, 'json') as AsciiCharacter
, @position as CharacterPosition
SET @position = @position + 1

SQL Server Non ascii characters

I wrote this with verbosity in mind to provide more detail about what the values are. The results of this will return the following:

9	\t	4
9	\t	5
13	\r	12
10	\n	13
9	\t	14

Good luck, this took me a while to build towards this final solution from incremental research of different functions and hopefully save someone the time. If you’re looking for my SQL tutorials this is a great next step CASE Statement in SQL (Practical Examples).

SQL replace: How to replace ASCII special characters in SQL Server?

A key part of ETL is transformation of sources of information. These may involve the look for new digits, conversion values between data types or just removing trailing spaces in an underlying database. A factor that can cause problems when transcribing source information is to eliminate ASCII printable characters types such as new line characters and vertical dividers. We also reviewed the user-defined functionality that can be used in cleaning up data from sources that contain ASCII special letters.

Replacing ASCII control characters

The ASCII standards define a list of ASCII-controlled character groups together as ASCII Control characters. This character is usually not easily identifiable (for a human being) therefore not easily replaced by the replacement function of T-SQL. Table 1 shows an example ASCII Control Character. In order to illustrate how challenging it is to clean ASCII character control codes in the C# console Script 4 has created the output file TXT. This document contains various variations of John’s email address (the first one has John Doe).

Replacing ASCII printable characters

Generally recognized standard codes of information exchange (ASCII) represent character numbers in computers. The ASCII number associated with the backslash () character is 93. Some software manufacturers use ASCII and therefore represent character codes with ASCII standards. Similar to SQL Server which utilizes ASCII, SQL Server includes the builtin printable CHAR function, which converts a numerical ASCII value into the original character.

How do I get non-ASCII characters in SQL?

In other cases regular expressions are used for non-ASCII character types. ASCII characters are captured with regex [A-ZaZ0-9]. This regex can be used to search non-ASCII numbers. MySQL > select * Using data whose full_name does not correspond to GEXP.

How do I find ASCII characters in SQL?

If you ever need to retrieve ASCII codes in SQL Server, then this T-SQL ASCII() method may be what you need. The ASCII() function returns the ASCII code of the leftmost character.

Where can I find non-ASCII characters?

If you want an easy way to replace non-ASCII or non printable characters you should use regexp [[:nonasci:]]. If you already have Emacs 20, you should be using regexes [000-177] to write code. Interactively, it is possible to apply cm-s CQ0 ‘0 CQ - CQ7’ RET. )

How do you find if a string contains special characters in SQL?

Links. Getting SQL Server’s characters “&” using like statements & wildcards. Check whether a particular character exists in SQL. Basic operations of similar operators. Check restrictions - check passwords must contain at least a number or special character - uppercase characters. -4.

How do I create a non printable character?

Inserting ASCII Characters When entering an ASCII character, hold down Alt while typing. To put the degree symbol in a text box you must press ALT when typing 0176 into a Numeric Keypad. It must be written on an alphabetic keypad instead of using a keyboard.

What characters are not allowed in SQL?

Noms may include any number of special characters: #, # or $. The name specified with denotes (in double quotes) may include extra special symbols.

How do I use Unicode characters in SQL?

SQL Server Unicode() function UnicoDE() functions return integer values (Unicode values) for the first characters in the output expression.

How do I select non-ASCII characters in SQL?

You can use these regexes for searching non-ASCII numbers.

Mysql> select * from data

when fullname is not REGEXP. For example, the table below does not contain an underscore.

What is a Unicode character?

Unicode encoding standards provide the unique number to each character across language and script making nearly the entire character accessible to the user across platform programs or mobile phones.

What is non Unicode characters in SQL?

SQL servers mainly separate string types from Unicodes to non Unicodes. This equates with nchar nvar - ntext and nchar for the Unicode characters and char var. We will now compare the category to choosing the best category for the next time.

What are the Unicode character data types?

Unicode identifiers. Unicode is stored as data of the type schar, nvarchars and long-numbers nvarchar. The letters are identical in appearance to characters such as chars, varchars, and long varchars respectively.

Published on Jul 25, 2022

Tags: SQL Tutorials for Beginners, Intermediate and Advanced Users | unicode

Related Posts

Did you enjoy this article? If you did here are some more articles that I thought you will enjoy as they are very similar to the article that you just finished reading.


Learn how to code in HTML, CSS, JavaScript, Python, Ruby, PHP, Java, C#, SQL, and more.

No matter the programming language you're looking to learn, I've hopefully compiled an incredible set of tutorials for you to learn; whether you are beginner or an expert, there is something for everyone to learn. Each topic I go in-depth and provide many examples throughout. I can't wait for you to dig in and improve your skillset with any of the tutorials below.