mysql 字符串取交集

SELECT DISTINCT tag
FROM (
    SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(tags, ',', numbers.n), ',', -1) AS tag
    FROM table1, (
        SELECT 1 n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
        UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10
    ) numbers
    WHERE LENGTH(tags) - LENGTH(REPLACE(tags, ',', '')) >= numbers.n - 1
) AS subquery
WHERE tag IN (
    SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(tags, ',', numbers.n), ',', -1) AS tag
    FROM table2, (
        SELECT 1 n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
        UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10
    ) numbers
    WHERE LENGTH(tags) - LENGTH(REPLACE(tags, ',', '')) >= numbers.n - 1
);

SELECT DISTINCT t1.tag
FROM (
    SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(tags, ',', numbers.n), ',', -1) AS tag
    FROM table1, (
        SELECT 1 n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
        UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10
    ) numbers
    WHERE LENGTH(tags) - LENGTH(REPLACE(tags, ',', '')) >= numbers.n - 1
) AS t1
JOIN (
    SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(tags, ',', numbers.n), ',', -1) AS tag
    FROM table2, (
        SELECT 1 n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
        UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10
    ) numbers
    WHERE LENGTH(tags) - LENGTH(REPLACE(tags, ',', '')) >= numbers.n - 1
) AS t2 ON t1.tag = t2.tag;