MySQL Hitung catatan yang cocok dari beberapa tabel

Cara lain untuk menulis ulang kueri ini.

Kelompokkan dan hitung di setiap tabel satu per satu, lalu gabung:

SELECT  a.id, 
        COALESCE(b.t1, 0) AS t1,
        COALESCE(c.t2, 0) AS t2,
        COALESCE(d.t3, 0) AS t3
FROM
        entity a
    LEFT JOIN
        ( SELECT ei,
                 COUNT(*) AS t1
          FROM table1
          GROUP BY ei
        ) AS b
            ON a.id = b.ei
    LEFT JOIN
        ( SELECT ei,
                 COUNT(*) AS t2
          FROM table2
          GROUP BY ei
        ) AS c
            ON a.id = c.ei
    LEFT JOIN
        ( SELECT ei,
                 COUNT(*) AS t3
          FROM table3
          GROUP BY ei
        ) AS d
            ON a.id = d.ei
  ;

Anda pasti harus menambahkan indeks pada (ei) pada masing-masing dari 3 tabel, jika Anda belum memilikinya.