MySQL case当then子句

Question

$this->db->select('a.diskusi_id, a.topik_id, a.diskusi_komentar, a.diskusi_file, a.pengguna_id');

$this->db->select('CASE WHEN a.pengguna_id LIKE "mhs%" THEN (select f.mahasiswa_id, f.mahasiswa_nama, f.mahasiswa_nim) WHEN a.pengguna_id LIKE "dos%" THEN (select g.dosen_id, g.dosen_nama, g.dosen_nidn)');

$this->db->where('CASE WHEN a.pengguna_id LIKE "mhs%" THEN a.pengguna_id = f.mahasiswa_id WHEN a.pengguna_id LIKE "dos%" THEN a.pengguna_id = g.dosen_id');

$query = $this->db->get('diskusi a, mahasiswa f, dosen g');

It gave an error:

near from "diskusi a, mahasiswa f, dosen g"

I want to relate that if a.pengguna_id like "mhs%" then take data from mahasiswa f and if a.pengguna_id like "dos%" then take data from dosen g. I am Using Codeigniter, but if you have some correction to SQL syntax I will try to understand.

Answer 1

Try profiling your model with

$this->output->enable_profiler(TRUE);

the check sql syntax with query result.