MySQL REPLACE multiple values

Question

I have data in a column that is causing problems. There are multiple bad characters I need to remove. I'd like to do this in the query.

On this question: MySQL string replace

I see where I can SELECT REPLACE(string_column, 'search', 'replace') as url but this only works for example replacing a / with //

I need to replace / with // and also & with && for example in a single query. What is the best way to achieve this?

Answer 1

If you are replacing multiple character then you need to use multiple replace in one query something as below. But if there are many characters to be replaced then its better to use application layer to handle it. In other words for few replacement its easy to use query but for many character replacement the query really becomes messy and ends up hard to read or change.

select
replace(
  replace(string_column,'/','//'),'&','&&'
)

Answer 2

If you are using MySQL Version 8+ then below is the built-in function that might help you better.

String	Replace	Output
w"w'w. ex%a&m:pl–ec)o(m	"'%&:)(–	www.example.com

MySQL Query:

SELECT REGEXP_REPLACE('w"w\'w. ex%a&m:p l–e.c)o(m', '[("\'%[:blank:]]&:–)]', '');

Almost for all bugging characters-

SELECT REGEXP_REPLACE(column, '[\("\'%[[:blank:]]&:–,#$@!;\\[\\]\)<>\?\*\^]+','')

MySQL built-in function ( MySQL version 8+ ): REGEXP_REPLACE (string, patterns, replace-with)

REGEXP_REPLACE gives you the facility to search multiple characters and replace them in one shot.

To find multiple characters, pattern is:

[
    (               -- open parenthesis     
    "               -- double quotes        
    \'              -- single quotes        
    %               -- percentage       
    [:blank:]       -- space                
    &               -- ampersand        
    :               -- colon
    –               -- non ASCII character  
    )               -- close parenthesis        
]

Notice the [:blank:] , this is a [:character_class:] and MySQL does support many names.

Character Class Name	Meaning
alnum	Alphanumeric characters
alpha	Alphabetic characters
blank	Whitespace characters
cntrl	Control characters
digit	Digit characters
graph	Graphic characters
lower	Lowercase alphabetic characters
print	Graphic or space characters
punct	Punctuation characters
space	Space, tab, newline, and carriage return
upper	Uppercase alphabetic characters
xdigit	Hexadecimal digit characters