MySQL extrae texto sin formato de datos html o PHP?

Si su contenido siempre comienza con etiquetas (etc.)

prueba esto:

SELECT * from table  WHERE colmn_name REGEXP  '>[^<]*mytext'; 

Otra forma es usar strip_tags — Elimina las etiquetas HTML y PHP de una cadena

<?php
$text = '<p>Test paragraph.</p><!-- Comment --> <a href="#fragment">Other text</a>';
echo strip_tags($text);
echo "\n";

// Allow <p> and <a>
echo strip_tags($text, '<p><a>');
?>

Salida del código anterior:

Test paragraph. Other text
<p>Test paragraph.</p> <a href="#fragment">Other text</a>

Advertencia ::Because strip_tags() does not actually validate the HTML, partial or broken tags can result in the removal of more text/data than expected.

Debes poner el código html en una variable, digamos $html_input

$html_input= "'<p>text between tag 'p'</p><span>text between 'span'</span>'";
$stripped_html = strip_tags($html_input);

// Now insert it into the table `text`
INSERT INTO `text` VALUES (1, $striped_html);

Puramente MYSQL camino:

CREATE FUNCTION `strip_tags`($str text) RETURNS text
BEGIN
    DECLARE $start, $end INT DEFAULT 1;
LOOP
    SET $start = LOCATE("<", $str, $start);
    IF (!$start) THEN RETURN $str; END IF;
    SET $end = LOCATE(">", $str, $start);
    IF (!$end) THEN SET $end = $start; END IF;
    SET $str = INSERT($str, $start, $end - $start + 1, "");
END LOOP;
END;

mysql> select strip_tags('<span>hel<b>lo <a href="world">wo<>rld</a> <<x>again<.');
+----------------------------------------------------------------------+
| strip_tags('<span>hel<b>lo <a href="world">wo<>rld</a> <<x>again<.') |
+----------------------------------------------------------------------+
| hello world again.                                                   |
+----------------------------------------------------------------------+
1 row in set

Referencia:Stackoverflow