文章目錄
- Day two
- 1.查詢結果去重？ **distinct**
- 2.避免笛卡爾積現象？
- 3.sql 92/99區別？
- 4.非等值連接 （省略了inner）
- 5.自連接
- 6.外連接
- 7.子查詢
- 8.union（可以將查詢結果集相加）
- 9.limit（重點）
- 10.多表連接示意圖
- 11.創建表 （建表語句）
- 12.數據類型
- 13.insert插入語句
- 14.創建表賦默認值 /刪除表
- 15.表的複製
- 16.將查詢結果插入到一張表中
- 17.修改數據 update
- 18.刪除數據
- 19.表結構的修改（不學）
- 20.CRUD
- 其餘兩天鏈接
- 看到最後的幫忙點個==贊==👍🙏 謝謝！
Day two
1.查詢結果去重？ distinct
mysql> select distinct job from emp;
distinct name1，name2 聯合去重
distinct 放在所有關鍵字的最前面
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-e53QQbcz-1589887307200)(C:\Users\Administrator\AppData\Roaming\Typora\typora-user-images\image-20200516091122966.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519215911795.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-a9FBat9s-1589887307207)(C:\Users\Administrator\AppData\Roaming\Typora\typora-user-images\image-20200516091313652.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519215926253.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-vZ6kVOe3-1589887307209)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516154433665.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220146453.png#pic_center)
2.避免笛卡爾積現象？
匹配次數不會減少，只不過顯示的是有效記錄！
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-nNmhADiB-1589887307223)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516164718923.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220232269.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
3.sql 92/99區別？
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-hsxk7AVo-1589887307230)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516165746622.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220253861.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-DLlYQKUl-1589887307265)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516165734797.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220321813.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
join 前面可以加 inner 內連接
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-sBg2II7M-1589887307269)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516170109503.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220347802.png#pic_center)
4.非等值連接 （省略了inner）
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-u8AenaK8-1589887307335)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516170749200.png)]!](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519220411657.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-zR3lTCeB-1589887307348)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516170801079.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221233863.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
5.自連接
特點： 一張表看做兩張表 自己連接自己
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-qm2Eupi5-1589887307355)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516173050875.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221253577.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-kFSKKqI4-1589887307360)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516173133146.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221311974.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-y9spi359-1589887307364)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200516173113893.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221328494.png#pic_center)
6.外連接
兩張表一個主表一個副表
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-nT821KAY-1589887307370)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517092856036.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221345765.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
右外連接 加right
左外連接 加left
多張表之間查詢 join
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-c7bmziSj-1589887307372)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517100208683.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221437519.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
7.子查詢
可以再 select from where 後加 select
8.union（可以將查詢結果集相加）
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-Yamd3QTo-1589887307376)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517150438155.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221504336.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
9.limit（重點）
-
limit 是mysql 特有的 oracle 中 類似的（rownum）
-
limit 取結果集中的部分數據 這時他的作用
-
語法機制
limit startindex ，length
startindex表示起始位置
length表示取幾個。
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-RPEVIXPv-1589887307381)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517151904577.png)]]()
-
limit 是 sql 中最後執行的語句
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-RPEVIXPv-1589887307381)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517151904577.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221526420.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-BTeOsjyn-1589887307395)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517152108173.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/2020051922154293.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-f9OZTrm9-1589887307399)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200517153124482.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221559757.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
10.多表連接示意圖
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-Ukzl7IKP-1589887307413)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/ad3df1c4ecc7d2dbe85f92cdde8ec9a731fdd20dc4c5629ecb372b21de26c682-1.jpg)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221835123.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
11.創建表 （建表語句）
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-UI9VU6fg-1589887307415)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518102137320.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221854796.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-VZRDNQjn-1589887307421)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518105811946.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221913780.png#pic_center)
12.數據類型
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-YD99kN2w-1589887307436)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518102501572.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221930400.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-QtZ3e2so-1589887307439)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518102825831.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519221945712.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
13.insert插入語句
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-7iznFHxR-1589887307446)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518113126733.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222003130.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-vl7pezkL-1589887307451)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518113146582.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222018242.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-UsHS4IMh-1589887307455)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518113631528.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222031391.png#pic_center)
插入字段省略不寫
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-Wn43X1YV-1589887307460)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518115338714.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222046531.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
一次插入多行數據
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-HyfCNOuA-1589887307490)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518115509122.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222102179.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
14.創建表賦默認值 /刪除表
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-MPlYQdeP-1589887307492)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518113843166.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222116853.png#pic_center)
15.表的複製
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-sx1lh5dh-1589887307495)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518115808241.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222131509.png#pic_center)
16.將查詢結果插入到一張表中
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-KJt5gNhU-1589887307503)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518115842979.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222144853.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
17.修改數據 update
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-kRIrkM7D-1589887307508)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518120525707.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222203233.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-wrNqOSn4-1589887307512)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518120554063.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222218957.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
更新所有數據
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-UHqiWbyU-1589887307516)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518120656993.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222234549.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
18.刪除數據
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-MyDiBobo-1589887307518)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518120855010.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222249985.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjQ5MjIz,size_16,color_FFFFFF,t_70#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-V7HrhBb6-1589887307526)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518173325790.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222312251.png#pic_center)
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-2viFcOE1-1589887307529)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518173417752.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222327290.png#pic_center)
19.表結構的修改（不學）
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-K7Zq7qQV-1589887307533)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518121803126.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222343574.png#pic_center)
20.CRUD
![[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-trNjd6im-1589887307536)(%E6%95%B0%E6%8D%AE%E5%BA%93%20MySQL.assets/image-20200518121838523.png)]](https://pic1.xuehuaimg.com/proxy/csdn/https://img-blog.csdnimg.cn/20200519222355580.png#pic_center)
其餘兩天鏈接
第一天鏈接：https://blog.csdn.net/qq_43649223/article/details/106221325
第三天鏈接：https://blog.csdn.net/qq_43649223/article/details/106225179
看到最後的幫忙點個贊👍🙏 謝謝！![在這裏插入圖片描述]()
