How i can Replace Only first Result in SQL Function

问题

I will ask about SQL replacement function.

I need to your bits of help. In Wordpress DB, I must change a little part. I want to replace first result only in a column. I will explain by giving an example,

My string is = "Hello XXX tomorrow we XXX will meeting in XXX Dubai, Do you want join us XXX ? "

My result must be like this= "Hello MMM tomorrow we XXX will meeting in XXX Dubai, Do you want join us XXX ? "

in this example, we putted MMM to first result of XXX . How i can do it ?

I tried below this code but, it replaced every XXX to MMM;

UPDATE wp_comments SET comment_content = REPLACE ( comment_content, 'XXX', 'MMM' ) WHERE `comment_ID`=334 LIMIT 1

回答1:

In MySQL < 8.0, where regexp_replace() and the-like are not supported, you can use string functions:

update wp_comments
set comment_content = concat(
    substr(comment_content, 1, locate('XXX', comment_content) - 1),
    'MMM',
    substr(comment_content, locate('XXX', comment_content) + 3)
) 
where comment_id = 334 and locate('XXX', comment_content) > 0

Demo on DB Fiddle:

comment_id | comment_content                                                               
---------: | :-----------------------------------------------------------------------------
       334 | Hello MMM tomorrow we XXX will meeting in XXX Dubai, Do you want join us XXX ?

回答2:

regexp_replace() can do what you want. It takes an optional argument which is the occurrence to replace:

UPDATE wp_comments
    SET comment_content = REGEXP_REPLACE( comment_content, 'XXX', 'MMM', 1, 1 )
    WHERE comment_ID = 334
    LIMIT 1;

来源：https://stackoverflow.com/questions/61159171/how-i-can-replace-only-first-result-in-sql-function

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