1掀鹅、 導(dǎo)入hellodb.sql生成數(shù)據(jù)庫(kù)
(1) 在students表中，查詢年齡大于25歲已卸，且為男性的同學(xué)的名字和年齡
MariaDB [hellodb]> select name,age from students where age > 25 and gender="M";
+--------------+-----+
| name | age |
+--------------+-----+
| Xie Yanke | 53 |
| Ding Dian | 32 |
| Yu Yutong | 26 |
| Shi Qing | 46 |
| Tian Boguang | 33 |
| Xu Xian | 27 |
| Sun Dasheng | 100 |
+--------------+-----+
7 rows in set (0.00 sec)
(2) 以ClassID為分組依據(jù)棵介，顯示每組的平均年齡
MariaDB [hellodb]> select stuid,name,avg(age),gender,classid,teacherid from students group by classid;
+-------+--------------+----------+--------+---------+-----------+
| stuid | name | avg(age) | gender | classid | teacherid |
+-------+--------------+----------+--------+---------+-----------+
| 24 | Xu Xian | 63.5000 | M | NULL | NULL |
| 2 | Shi Potian | 20.5000 | M | 1 | 7 |
| 1 | Shi Zhongyu | 36.0000 | M | 2 | 3 |
| 5 | Yu Yutong | 20.2500 | M | 3 | 1 |
| 4 | Ding Dian | 24.7500 | M | 4 | 4 |
| 6 | Shi Qing | 46.0000 | M | 5 | NULL |
| 9 | Ren Yingying | 20.7500 | F | 6 | NULL |
| 8 | Lin Daiyu | 19.6667 | F | 7 | NULL |
+-------+--------------+----------+--------+---------+-----------+
8 rows in set (0.00 sec)
(3) 顯示第2題中平均年齡大于30的分組及平均年齡
MariaDB [hellodb]> select avg(age),classid from students group by classid having avg(age) > 30;
+----------+---------+
| avg(age) | classid |
+----------+---------+
| 63.5000 | NULL |
| 36.0000 | 2 |
| 46.0000 | 5 |
+----------+---------+
3 rows in set (0.00 sec)
(4) 顯示以L開(kāi)頭的名字的同學(xué)的信息
MariaDB [hellodb]> select * from students where name like "l%";
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
+-------+-------------+-----+--------+---------+-----------+
3 rows in set (0.00 sec)
2、數(shù)據(jù)庫(kù)授權(quán)magedu用戶缓升，允許192.168.1.0/24網(wǎng)段可以連接mysql
#授權(quán)magedu
MariaDB [(none)]> grant all on *.* to magedu@'192.168.1.%' identified by '123456';
Query OK, 0 rows affected (0.00 sec)
MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.00 sec)
#驗(yàn)證
[root@ka2 ~]# mysql -umagedu -p123456 -h192.168.1.177
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 3
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.02 sec)
MariaDB [(none)]> select host,user,password from mysql.user;
+--------------+--------+-------------------------------------------+
| host | user | password |
+--------------+--------+-------------------------------------------+
| localhost | root | |
| centos7.6 | root | |
| 127.0.0.1 | root | |
| ::1 | root | |
| 192.168.1.% | magedu | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+--------------+--------+-------------------------------------------+
3鼓鲁、總結(jié)mysql常見(jiàn)的存儲(chǔ)引擎以及特點(diǎn)。
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**MyISAM引擎特點(diǎn) **
不支持事務(wù)
表級(jí)鎖定
讀寫相互阻塞港谊，寫入不能讀骇吭，讀時(shí)不能寫
只緩存索引
不支持外鍵約束
不支持聚簇索引
讀取數(shù)據(jù)較快，占用資源較少
不支持MVCC（多版本并發(fā)控制機(jī)制）高并發(fā)
崩潰恢復(fù)性較差
MySQL5.5.5前默認(rèn)的數(shù)據(jù)庫(kù)引擎 InnoDB引擎特點(diǎn)
行級(jí)鎖
支持事務(wù)歧寺，適合處理大量短期事務(wù)
讀寫阻塞與事務(wù)隔離級(jí)別相關(guān)
可緩存數(shù)據(jù)和索引
支持聚簇索引
崩潰恢復(fù)性更好
支持MVCC高并發(fā)
從MySQL5.5后支持全文索引
從MySQL5.5.5開(kāi)始為默認(rèn)的數(shù)據(jù)庫(kù)引擎
