我只是漫遊是以下查詢有效。我有一張名爲教授的表格,其中包含教授。表主題包含主題。包含professor_id和subject_id字段的professor_subject表實現了多對多關係。這是SQL查詢有效(多對多關係)
現在我需要看看哪位教授正在教授哪個科目。我寫了這個SQL查詢:
SELECT concat(professor.name, " ", professor.surname) as "Professor",
subject.name as "Subject"
FROM professor_subject, subject, professor
WHERE subject.id = subject_id
and professor.id = professor_id;
該查詢是否有效?我的意思是,它會一直做我想要的嗎?我有點可疑,因爲我沒有使用JOIN關鍵字。
謝謝:)
儘管Justin Niessner的回答是正確的,但您並不一定需要JOIN關鍵字來進行連接。你可以把他的解答也寫成'select concat(professor.name,「,professor.surname)作爲」Professor「,subject.name作爲」Subject「 from Professor,subject,professor_subject where professor.id = professor_subject.professor_id and professor_subject.subject_id = subject.id' – 2012-04-25 15:45:20
@AlexMonthy:這就是我寫的,除了我很懶,所以我忽略了「professor_subject」。在subject_id和professor_id之前:) – xx77aBs 2012-04-25 15:49:14