如何从多个连接表 MySQL 中选择不同的最大值

Question

这是我当前用于选择数据的查询：

select a.No_Registrasi, a.Nama_CTKI, b.Nama_Negara, c.ID_Rad, d.ID_Lab
FROM tb_registrasi a 
JOIN tb_negara_tujuan b
    ON a.ID_Negara = b.ID_Negara
JOIN tb_radiologi c
    ON a.No_Registrasi = c.No_Registrasi
JOIN tb_laboratorium d
    ON a.No_Registrasi = d.No_Registrasi

结果如下：

我如何区分那些 ID_Rad 和 ID_Lab，我需要每个 ID_Rad 和 ID_Lab 的最大值，所以它会是这样的：

Answer 1

使用GROUP BY 和MAX，试试这个；）

select a.No_Registrasi, a.Nama_CTKI, b.Nama_Negara, CONCAT('RA-', MAX(substring(c.ID_Rad, 4) + 0)) AS ID_Rad, CONCAT('Lab-',MAX(substring(d.ID_Lab, 5) + 0)) AS Id_Lab
FROM tb_registrasi a 
JOIN tb_negara_tujuan b
    ON a.ID_Negara = b.ID_Negara
JOIN tb_radiologi c
    ON a.No_Registrasi = c.No_Registrasi
JOIN tb_laboratorium d
    ON a.No_Registrasi = d.No_Registrasi
GROUP BY a.No_Registrasi, a.Nama_CTKI, b.Nama_Negara