Random samples of 100 musician articles in all quality classes

SQL

USE enwiki_p;
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "Stub" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "Stub-Class_biography_(musicians)_articles" 
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title
UNION ALL
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "Start" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "Start-Class_biography_(musicians)_articles" 
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title
UNION ALL
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "C" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "C-Class_biography_(musicians)_articles"  
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title
UNION ALL
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "B" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "B-Class_biography_(musicians)_articles"  
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title
UNION ALL
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "GA" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "GA-Class_biography_(musicians)_articles"  
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title
UNION ALL
SELECT
  tp.page_title, class, article.page_len, article.page_latest
FROM (
  SELECT cl_from, "FA" AS class 
  FROM categorylinks qual 
  WHERE qual.cl_to = "FA-Class_biography_(musicians)_articles"  
  ORDER BY RAND()
  LIMIT 100
) AS foo
INNER JOIN page tp ON cl_from = page_id
INNER JOIN page article ON article.page_namespace = 0 AND article.page_title = tp.page_title
GROUP BY tp.page_title;
SQL

Checking query status...
