MySQL get string(s) between two # / multiple pairs of #

Question

How can I find string between two # or multiple pairs of #.

An example text to search: This is #important# and needs to elaborated further. Remember to buy #milk be

Answer 1

You can try this code

<?php
    $s =  'This is #important# and needs to elaborated further. Remember to buy #milk before coming home#';
    for($i=0;$i<strlen($s);$i++)
        if($s[$i] == "#") {
        $i++;
        $str="";
        while($s[$i]!='#') {
            echo $s[$i];
            $i++;
        }
        echo '<br>';
    };
    ?>

then you will get your result

important

milk before coming home

Answer 2

Edit 1

create table t91
(   id int auto_increment primary key,
    thing varchar(1000) not null
);
insert t91(thing) values
('This is #important# and needs to elaborated further. Remember to buy #milk before coming home#'),
('This is #important# and needs to elaborated further. Remember to buy #milk home#'),
('This is #');


select id,thing,theCount
from
(   SELECT id,thing,
        ROUND (   
            (
                LENGTH(thing)
                - LENGTH( REPLACE ( thing, "#", "") ) 
            ) / LENGTH("#")        
        ) AS theCount    
    FROM t91
) d
where d.theCount>1
-- 2 rows returned (id 1 and 2)

The above Edit used a strategy poached from This Answer

Edit2

-- truncate table t91;
create table t91
(   id int auto_increment primary key,
    thing varchar(1000) not null
);
insert t91(thing) values
('This is #important# and needs to elaborated further. Remember to buy #milk before coming home#'),
('This is #important# and needs to elaborated further. Remember to buy #milk home#'),
('This is #'),
('This is #1# ... #2# ... #');

Function:

DROP FUNCTION IF EXISTS findInsideHashMarks;
DELIMITER $$
CREATE FUNCTION findInsideHashMarks(s VARCHAR(200),segments INT)
RETURNS VARCHAR(200)
BEGIN
    DECLARE i,nextPos,i1,i2 INT;
    DECLARE sOut VARCHAR(200);
    SET i=0;
    SET nextPos=1;
    SET sOut='';
    WHILE i<segments DO
        -- LOCATE(substr,str,pos)
        SET i1=LOCATE('#',s,nextPos);
        IF i1>0 THEN
            SET i1=i1+1;
            SET nextPos=i1+1;
            SET i2=LOCATE('#',s,nextPos);
            IF i2>0 THEN
                SET nextPos=i2+1;
                SET i2=i2-1;
                SET sOut=CONCAT(sOut,SUBSTRING(s,i1,i2-i1+1));
            END IF;
        END IF;
        SET i=i+1;
        IF i<segments THEN
            SET sOut=CONCAT(sOut,',');
        END IF;
    END WHILE;
    RETURN sOut;
END$$
DELIMITER ;

Query:

SELECT id,
SUBSTRING_INDEX(SUBSTRING_INDEX(segString, ',', n.digit+1), ',', -1) dummy
FROM
(   select id,thing,theCount,cast(floor(theCount / 2) as unsigned) as segments,
    findInsideHashMarks(thing,cast(floor(theCount / 2) as unsigned)) as segString
    FROM
    (   SELECT id,thing,
            ROUND (   
                (   LENGTH(thing)
                    - LENGTH( REPLACE ( thing, "#", "") ) 
                ) / LENGTH("#")        
            ) AS theCount    
        FROM t91
    ) d1
    where d1.theCount>1
) d2
INNER JOIN
(SELECT 0 digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3) n
ON LENGTH(REPLACE(d2.segString, ',' , '')) <= LENGTH(d2.segString)-n.digit
ORDER BY d2.id,n.digit;

Output:

+----+-------------------------+
| id | dummy                   |
+----+-------------------------+
|  1 | important               |
|  1 | milk before coming home |
|  2 | important               |
|  2 | milk home               |
|  4 | 1                       |
|  4 | 2                       |
+----+-------------------------+

The digits breakout of a set (a,b,c) to rows was inspired (understatement) by this Answer from User fthiella. As noted in that Answer from fthiella (or not expressly so), the UNION strategy could be expanded to pick up, say, 10 or more chunks of data between # markers.

Also note the prior attribution at the bottom of Edit1.

Edit3

An offshoot off of Edit2's function and query, but using a permanent Helper Table to avoid the UNION in the query for derived table n. It supports up to 100 # segments. Uses the prior (Edit2) t91 table and the Function.

Schema:

CREATE TABLE 4kTable
(   -- a helper table of about 4k consecutive ints
    id int auto_increment primary key,
    thing int null
)engine=MyISAM;

insert 4kTable (thing) values (null),(null),(null),(null),(null),(null),(null),(null),(null);
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
insert 4kTable (thing) select thing from 4kTable;
-- verify:
-- select min(id),max(id),count(*) from 4kTable;
-- 1 4608 4608

ALTER TABLE 4kTable ENGINE = InnoDB; -- *********** it is now InnoDB

-- verify:
-- select min(id),max(id),count(*) from 4kTable;
-- 1 4608 4608
-- no innodb auto_increment gaps (consecutive block)

Query:

SELECT id, 
SUBSTRING_INDEX(SUBSTRING_INDEX(segString, ',', n.digit+1), ',', -1) dummy 
FROM 
(   select d1.id,thing,theCount,cast(floor(theCount / 2) as unsigned) as segments, 
    findInsideHashMarks(thing,cast(floor(theCount / 2) as unsigned)) as segString 
    FROM 
    (   SELECT id,thing, 
            ROUND (   
                (   LENGTH(thing) 
                    - LENGTH( REPLACE ( thing, "#", "") )  
                ) / LENGTH("#")         
            ) AS theCount     
        FROM t91 
    ) d1 
    where d1.theCount>1 
) d2 
INNER JOIN
(select id-1 as digit from 4kTable where id<=100) n
ON LENGTH(REPLACE(d2.segString, ',' , '')) <= LENGTH(d2.segString)-n.digit
ORDER BY d2.id,n.digit;

Same output as above Edit2 Output section. I usually have a few permanent Helper Tables in a system, especially for left joins with dates.