SELECT

    extracted_bold_word

FROM

    (SELECT

        SUBSTRING_INDEX(old_text, '.', 1) AS first_sentence,

        page_title

     FROM page

     INNER JOIN slots ON page_latest = slot_revision_id

     INNER JOIN slot_roles ON slot_role_id = role_id AND role_name = 'main'

     INNER JOIN content ON slot_content_id = content_id

     INNER JOIN text ON substring(content_address, 4) = old_id AND left(content_address, 3) = 'tt:'

    ) AS sentences

CROSS JOIN LATERAL -- Use LATERAL JOIN to process each row from 'sentences' independently

    (SELECT

        REPLACE(REPLACE(extracted_word_list.val, '''', ''), '_', ' ') as extracted_bold_word

        FROM

        (SELECT

            -- Extract all bolded words using REGEXP_EXTRACT_ALL (MariaDB 10.6+)

            -- For older versions, a different approach would be needed (more complex)

            JSON_TABLE(

                REGEXP_EXTRACT_ALL(sentences.first_sentence, '''([^''']+)''' ), -- Extracts content between ''' and '''

                '$[*]' COLUMNS (val VARCHAR(255) PATH '$')

            ) AS extracted_word_list

         ) AS extracted_word_table

     ) AS bold_words

WHERE extracted_bold_word IS NOT NULL AND extracted_bold_word <> ''

HAVING

    NOT EXISTS (

        SELECT 1

        FROM page AS p2

        WHERE LOWER(p2.page_title) = LOWER(extracted_bold_word)

    );