數據庫關聯查詢說明

原創 GOon_star 2020-02-23 05:33

關聯查詢包括：內連接 外連接 全連接 交叉連接（即笛卡爾積）

內連接：只連接匹配的行。

外連接

       左外連接：左邊表的全部數據和所連接表的符合連接條件的數據。

       右外連接：與左連接相反，連接表的全部數據和左邊表符合連接條件的數據。

      全外連接：又稱全連接，即兩個表的全部數據。

theta連接

     取兩個表的不匹配的行。同內連接相反。

笛卡爾積

     即其中一個表同另一個表的所有行進行匹配連接。

發表評論
所有評論
還沒有人評論，想成為第一個評論的人麼? 請在上方評論欄輸入並且點擊發布.
相關文章

一場數據架構變革正在來臨

{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null

蔡芳芳 2021-12-21 10:54:01

解讀數字化轉型下的數據安全：AI正在開闢新的可能性

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

凌敏 2021-12-19 14:03:54

雲原生數據庫企業Cockroach Labs再獲 2.73 億美元融資，估值高達50億美元

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

Tina 2021-12-16 15:18:50

數千個數據庫、遍佈全國的物理機，京東物流全量上雲實錄 | 卓越技術團隊訪談錄

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":1}},{"type":"blockquote","content":[{"type":"pa

褚杏娟 2021-12-16 10:38:55

前車之鑑：聊聊我在基礎設施中掉過的坑

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

Mathew Duggan 2021-12-14 13:33:55

洞察數據庫變革趨勢，亞馬遜雲科技正在憑藉這項技術改變着遊戲規則

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

李冬梅 2021-12-10 16:53:54

MongoDB發佈第三季度財報，雲數據庫收入增長加速

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

Tina 2021-12-09 15:33:57

MySQL探祕(四):InnoDB的磁盤文件及落盤機制

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

程序员历小冰 2021-12-08 12:33:52

Oracle 大佬離職，怒噴 MySQL “糟糕的數據庫”

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

辛晓亮 2021-12-07 19:58:57

Jellyfish：爲Uber最大的存儲系統提供更節省成本的數據分層

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

Mohammed Khatib 2021-12-06 10:33:48

企業需要什麼樣的數據庫，One Size Fits All？

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

张俊宝 2021-12-03 18:19:01

這個重要開源項目全靠一位低調的“怪老頭”維護！他和比爾蓋茨一樣撐起了計算機世界

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

张健欣 2021-12-03 14:23:56

數據庫事務的三個元問題

{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null

Zilliz 2021-12-03 10:33:52

一個 Babelfish ，看懂雲數據庫的發展方向

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":1}},{"type":"paragraph","attrs":{"indent":0,"nu

王一鹏 2021-12-01 18:43:50

數據庫內核雜談(二十一): 流處理系統簡介

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"typ

顾仲贤 2021-11-24 10:38:57