Replace random word - mysql

Question

I want replace random word in WordPress post. I have a code for MySQL.
This code working well:
update wp_posts set post_content =
replace(post_content,'oldword','newword');
But when I want replace random in database like
replace(post_content,'oldword',rand('newword','google','stackoverflow','stackover'));
This code not working.
I don't know how use this code for random replace word.
I want each occurrence of oldword to be replaced by a different word
Error
SQL query:
UPDATE wp_posts SET post_content =
REPLACE_RANDOM(post_content, 'oldword')
MySQL said: Documentation
#1366 - Incorrect string value: '\xD8\xA7\xDB\x8C\xD9\x86...' for column 'String' at row 1
Where is the problem?
DELIMITER $$
DROP FUNCTION IF EXISTS Replace_Random$$
CREATE FUNCTION Replace_Random(String TEXT, Word TEXT)
RETURNS TEXT
BEGIN
DECLARE New TEXT DEFAULT '';
DECLARE Loc INT DEFAULT INSTR(String, Word);
DECLARE WLen INT DEFAULT Length(Word);
WHILE Loc DO
SET New = CONCAT(New, SUBSTR(String, 1, Loc-1), ELT(FLOOR(RAND()*5)+1, 'biterrr', 'stackoverflow', 'serress', 'ms-ms-ms', 'Nick'));
SET String = SUBSTR(String, Loc + WLen);
SET Loc = INSTR(String, Word);
END WHILE;
SET NEW = CONCAT(New, String);
RETURN New;
END$$
DELIMITER ;
UPDATE wp_posts SET post_content =
REPLACE_RANDOM(post_content, 'oldword');`

Answer 1

You could use ELT to pick a random value from a list of strings:
UPDATE wp_posts SET post_content =
REPLACE(post_content, 'oldword', ELT(FLOOR(RAND()*5)+1, 'hello', 'world', 'friend', 'tuesday', 'sunny'))
If you have a different number of strings in the list, just change the multiplier of RAND() from 5 to the number of strings.
Update
If you need to replace multiple occurrences of the string in a phrase with different words, you will need a stored function. This one will do the job:
DELIMITER \\
DROP FUNCTION IF EXISTS Replace_Random\\
CREATE FUNCTION Replace_Random(String TEXT CHARACTER SET utf8, Word TEXT CHARACTER SET utf8)
RETURNS TEXT CHARACTER SET utf8
BEGIN
DECLARE New TEXT CHARACTER SET utf8 DEFAULT '';
DECLARE Loc INT DEFAULT INSTR(String, Word);
DECLARE WLen INT DEFAULT Length(Word);
WHILE Loc DO
SET New = CONCAT(New, SUBSTR(String, 1, Loc-1), ELT(FLOOR(RAND()*5)+1, 'hello', 'world', 'friend', 'tuesday', 'sunny'));
SET String = SUBSTR(String, Loc + WLen);
SET Loc = INSTR(String, Word);
END WHILE;
SET NEW = CONCAT(New, String);
RETURN New;
END\\
DELIMITER ;
SELECT REPLACE_RANDOM('a string with oldword in it twice - oldword!', 'oldword');
Output (varies):
a string with sunny in it twice - tuesday!
a string with hello in it twice - friend!