SQL Group By - Hasilkan beberapa kolom agregat dari satu kolom

Anda dapat melakukannya menggunakan subkueri berkorelasi seperti ini:

SELECT 
  Company, 
  Date, 
  (SELECT COUNT(*) FROM MyTable AS T1 
     WHERE T1.Flag='Y' AND T1.Company=T2.Company AND T1.Date=T2.Date) AS Count_Y,
  (SELECT COUNT(*) FROM MyTable AS T1 
     WHERE T1.Flag='N' AND T1.Company=T2.Company AND T1.Date=T2.Date) AS Count_N
FROM MyTable AS T2
GROUP BY Company, Date

Anda juga dapat melakukannya dengan lebih ringkas, tetapi mungkin dengan (bisa dibilang) kurang mudah dibaca menggunakan SUM trik:

SELECT 
  Company, 
  Date, 
  SUM(CASE WHEN Flag='Y' THEN 1 ELSE 0 END) AS Count_Y,
  SUM(CASE WHEN Flag='N' THEN 1 ELSE 0 END) AS Count_N,
FROM MyTable
GROUP BY Company, Date

Di Oracle/PLSQL, DECODE fungsi dapat digunakan untuk menggantikan CASE untuk yang lebih ringkas:

SELECT 
  Company, 
  Date, 
  SUM(DECODE(Flag,'Y',1,0)) AS Count_Y,
  SUM(DECODE(Flag,'N',1,0)) AS Count_N,
FROM MyTable
GROUP BY Company, Date