Aggregates of specified size

from the Artful Common Queries page


Find the values of a table column c1 for which there are a specified number of listed values in another column c2. To get an overview of the values of c2 for each value of c1:
SELECT
  c1, 
  GROUP_CONCAT(c2 ORDER BY c2) AS 'C2 values'
FROM table
GROUP BY c1;
To retrieve a list of c1 values for which there exist specific values in another column c2, you need an IN clause specifying the c2 values and a HAVING clause specifying the required number of different items in the list ...
SELECT c1 
FROM table
WHERE c2 IN (1,2,3,4)
GROUP BY c1
HAVING COUNT(DISTINCT c2)=4;
This is easy to generalise to multiple column expressions, and a HAVING clause specifying any number of items from the IN list.

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