From a2863cecaa4c7641116cdd058b1aed551f42d450 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=BE=88=E7=8B=87?= <1706442984@qq.com>
Date: Mon, 21 Oct 2024 00:39:05 +0800
Subject: [PATCH] =?UTF-8?q?feat:=E4=BD=9C=E4=B8=9A?=
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@@ -0,0 +1,43 @@
+```sql
+SELECT * FROM `emp`
+-- 练习和作业 
+-- 1.给emp分别建立 普通索引和唯一索引
+CREATE INDEX idx on emp(empno);
+CREATE UNIQUE index idxs on emp(empno);
+SHOW index FROM emp;
+-- 2.查询emp表有哪些索引
+SHOW index FROM emp;
+-- 3. 使用有索引的字段进行查询，再查看这条语句是否使用到了索引。
+SELECT * FROM emp WHERE ename = '庞统';
+ EXPLAIN SELECT * FROM emp WHERE ename = '庞统';
+-- 4. 删除前面建立的两个索引
+ALTER TABLE emp DROP INDEX idx;
+ALTER TABLE emp DROP INDEX idxs;
+-- 5. 选择两个字段添加一个复合索引
+CREATE INDEX idx ON emp(empno,ename);
+-- 6. 使用复合索引的字段进行查询
+SELECT * FROM emp WHERE empno=1001 AND ename='甘宁';
+
+
+```
+
+```sql
+-- 作业
+-- 想办法用自己的电脑，生成500万行数据,id,uname,age 尽量随机，并记录时间。
+```
+
+
+
+![11](https://gitee.com/ChemuWare/gstxmm/raw/master/photo/202410210028496.png)
+
+```sql
+-- 1. 不用索引查询 一次姓名uname /并记录时间
+```
+
+![image-20241021003711691](https://gitee.com/ChemuWare/gstxmm/raw/master/photo/202410210037738.png)
+
+```sql
+-- 2. 建立索引查询 一次姓名uname /并记录时间
+```
+
+![image-20241021003826179](https://gitee.com/ChemuWare/gstxmm/raw/master/photo/202410210038268.png)
-- 
Gitee