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由MySQL AB公司開發，是最流行的開放源碼SQL數據庫管理系統，主要特點：
1、是一種數據庫管理系統
2、是一種關聯數據庫管理系統
3、是一種開放源碼軟件，且有大量可用的共享MySQL軟件
4、MySQL數據庫服務器具有快速、可靠和易于使用的特點
5、MySQL服務器工作在客戶端/服務器模式下，或嵌入式系統中
2.1. 單字段：
PRIMARY KEY 主鍵
UNIQUE KEY 唯一鍵
2.2 單或者多字段：
PRIMARY KEY(col,...)
UNIQUE KEY(col,...)
INDEX(col,...)
2.3 數據類型：
BIT[(length)] 比特
| TINYINT[(length)] [UNSIGNED] [ZEROFILL] 非常小的整數（1字節）
| SMALLINT[(length)] [UNSIGNED] [ZEROFILL] 小的整數（2字節）
| MEDIUMINT[(length)] [UNSIGNED] [ZEROFILL] 中等的整數（3字節）
| INT[(length)] [UNSIGNED] [ZEROFILL] 整數（4字節）
| INTEGER[(length)] [UNSIGNED] [ZEROFILL] 整數（4字節）相當于INT
| BIGINT[(length)] [UNSIGNED] [ZEROFILL] 大的整數（8個字節）
| REAL[(length,decimals)] [UNSIGNED] [ZEROFILL] 實數
| DOUBLE[(length,decimals)] [UNSIGNED] [ZEROFILL] 雙精度整型
| FLOAT[(length,decimals)] [UNSIGNED] [ZEROFILL] 浮點型
| DECIMAL[(length[,decimals])] [UNSIGNED] [ZEROFILL]十進制小數點型
| NUMERIC[(length[,decimals])] [UNSIGNED] [ZEROFILL]數值型
時間：
| DATE 日期型
| TIME 時間型
| TIMESTAMP 時區型
| DATETIME 日期時間型
| YEAR 年
| CHAR[(length)] 定長字符型 255 characters
VARCHAR(length) 變長字符型 65535 characters
[CHARACTER SET charset_name] [COLLATE collation_name]
| BINARY[(length)] 二進制數
| VARBINARY(length) 變長二進制數
| TINYBLOB 非常小的大對數
| BLOB 大對數
| MEDIUMBLOB 中等的大對數
| LONGBLOB 長的大對數
文本：（不大小寫）
| TINYTEXT [BINARY] 非常小的文本串 255 characters 2~8
[CHARACTER SET charset_name] [COLLATE collation_name]
| TEXT [BINARY] 文本串 65535 characters 2~16
[CHARACTER SET charset_name] [COLLATE collation_name]
| MEDIUMTEXT [BINARY] 中等的文本串 16,777,215 characters 2~24
[CHARACTER SET charset_name] [COLLATE collation_name]
| LONGTEXT [BINARY] 長的文本串 4,294,967,295 characters 2~32
[CHARACTER SET charset_name] [COLLATE collation_name]
| ENUM(value1,value2,value3,...) 枚舉型
[CHARACTER SET charset_name] [COLLATE collation_name]
| SET(value1,value2,value3,...) 集合型
[CHARACTER SET charset_name] [COLLATE collation_name]
| spatial_type 空間的類型
2.4、創建數據庫：
CREATE DATABASE|SCHEMA [IF NOT EXISTS] db_name [CHARACTER SET=] [COLLATE]
創建數據庫可以設置字符集，排序規則
mysql> SHOW CHARACTER SET; #查看字符集
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
.......
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
........
39 rows in set (0.00 sec)
mysql> SHOW COLLATION; #查看排序規則
+-------------------+----------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+-------------------+----------+-----+---------+----------+---------+
| big5_chinese_ci | big5 | 1 | Yes | Yes | 1 |
| big5_bin | big5 | 84 | | Yes | 1 |
| cp1250_polish_ci | cp1250 | 99 | | Yes | 1 |
...
197 rows in set (0.00 sec)
mysql> show global variables like '%char%';
+------------------+-----------------+
| Variable_name | Value |
+------------------+----------------+
| character_set_client | latin1 |
| character_set_connection | latin1 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | latin1|
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
8 rows in set (0.00 sec)
mysql> CREATE DATABASE IF NOT EXISTS students CHARACTER SET 'gbk' COLLATE 'gbk_chinese_ci';
#創建一個students數據庫，字符集為gbk，排序規則為gbk_chinese_ci
Query OK, 1 row affected (0.01 sec)
mysql> \q
Bye
[root@lamp ~]# ls /mydata/data #查看students是否新建成功
ib_logfile1 mysql-bin.000001 mysql-bin.000006 mysql-bin.000011 students
[root@lamp ~]# file /mydata/data/students/db.opt #查看students數據庫中db.opt文件類型
/mydata/data/students/db.opt: ASCII text
2.5、修改數據庫：
ALTER {DATABASE | SCHEMA} [db_name] alter_specification ...#修改數據庫的屬性，比如字符集或者排序規則，alter_specification CHARACTER SET = charset_name COLLATE = collation_name
alter_specification包含:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
ALTER {DATABASE | SCHEMA} db_name UPGRADE DATA DIRECTORY NAME #升級數據庫的數據目錄
2.6、刪除數據庫：
DROP {DATABASE | SCHEMA} [IF EXISTS] db_name #刪除數據庫
2.7、創建表：
2.7.1.直接定義一張空表；col_name 字段名稱 col_defination 字段定義
CREATE TABLE [IF NOT EXISTS] tb_name (col_name col_defination,)
col_defination字段定義包含：data_type字段類型
data_type [NOT NULL | NULL] [DEFAULT default_value]
[AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
[COMMENT 'string']
[COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
[STORAGE {DISK|MEMORY|DEFAULT}]
[reference_definition]
Usage:CREATE TABLE tb1(id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,Name CHAR(20) NOT NULL,Age TINYINT NOT NULL);
#創建一個表tb1，包含三個字段:
id字段為無符號(UNSIGNED)，非空(NOT NULL)，自動增長(AUTO_INCREMENT)，為主鍵(PRIMARY KEY)的整型.
Name字段為定長20(CHAR(20)),非空的字符型。
Age字段為非空的非常小的整型。
或者 CREATE TABLE tb2(id INT UNSIGNED NOT NULL AUTO_INCREMENT,Name CHAR(20) NOT NULL,Age TINYINT NOT NULL,PRIMARY KEY(id),Unique KEY (Name),INDEX(age)); #Unique KEY 唯一鍵，INDEX索引
2.7.2.從其他表中查詢出數據，并以之創建新表；
CREATE TABLE testcourses SELECT * FROM courses WHERE CID <= 2;
#從courses表中查找CID小于等于2的數據，并作為新建testcourses表的內容。
2.7.3.以其他表為模板創建一個空表；
查看表索引：
SHOW INDEXES FROM courses; 顯示制定表索引
查看表結構：
DESC tb_name; 查看表結構
mysql> DESC courses;
+-------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+----------------+
| CID | tinyint(3) unsigned | NO | PRI |NULL|auto_increment|
| Couse | varchar(50) | NO | | NULL | |
2 rows in set (0.00 sec)
2.8、修改表定義：ALTER TABLE
添加、刪除、修改字段，添加、刪除、修改索引，改表名，修改表屬性。
mysql> ALTER TABLE test ADD INDEX(Couse); #給test表增加以Couse字段為索引
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW INDEXES FROM test; #查看test表的索引
+------+-------+-------+------+------+-------+-------+-------+------+------+-------+-------+-------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+------+-------+-------+------+------+-------+-------+
| test | 0 | PRIMARY | 1 | CID | A | 0 | NULL | NULL | | BTREE | | |
| test | 1 | Couse | 1 | Couse | A | NULL | NULL | NULL | | BTREE | | |
2 rows in set (0.00 sec)
mysql> DESC test; #查看表結構
+-------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------------+------+
| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |
| Couse | varchar(50) | NO | MUL | NULL | |
2 rows in set (0.00 sec)
mysql> ALTER TABLE test CHANGE Couse Course VARCHAR(50) NOT NULL; #修改test表的Couse字段名稱為Course并定義為變長50字符長度，非空
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> DESC test; 查看表結構
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+
| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |
| Course | varchar(50) | NO | MUL | NULL | |
2 rows in set (0.00 sec)
mysql> DROP TABLE testcourses; #刪除testcourses表
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW TABLES;查看所有表
+--------------------+
| Tables_in_students |
+--------------------+
| courses |
| test |
+--------------------+
2 rows in set (0.00 sec)
mysql> ALTER TABLE test RENAME TO testcourses; #修改test表的名稱為testcourses
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW TABLES;查看所有表
+--------------------+
| Tables_in_students |
+--------------------+
| courses |
| testcourses |
2 rows in set (0.00 sec)
mysql> RENAME TABLE testcourses TO test; #也可以直接使用RENAME重命名。
Query OK, 0 rows affected (0.00 sec)
2.9、新增索引：（索引只能新建刪除，不能修改）
CREATE INDEX index_name ON tb_name (col,...) col_name (length) ASC|DESC
指定以字段前幾的長度為索引，ASC升序排列，DESC降序排列。
在tb_name表上的col字段創建一個索引index_name
CREATE INDEX name_on_student ON student (Name) USING BTREE;
#在student表中Name字段上建立一個名為name_on_student索引，類型為BTREE索引，默認為BTREE類型。
mysql> CREATE INDEX name_on_student ON student (Name) USING BTREE ;
mysql> SHOW INDEXES FROM student ;
+---------+------------+-----------------+--------------+-------------+-----------+-------------+
| Table | Non_unique | Key_name| Seq_in_index|Column_name|Collation|Cardinality| Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+-----------------+--------------+
| student | 0 | PRIMARY | 1 | SID | A| 4 |NULL | NULL| | BTREE| | |
| student | 1 |foreign_cid| 1 | CID | A| 4 |NULL | NULL| | BTREE | | |
| student | 1 |name_on_student| 1 | Name| A| 4 | NULL | NULL| YES| BTREE | | |
3 rows in set (0.00 sec)
mysql> DROP INDEX name_on_student ON student;#刪除student表中的索引name_on_student
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> CREATE INDEX name_on_student ON student (Name(5) DESC);#為student表以Name字段
的前5個字符建立一個降序（DESC）排列的索引.
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
實例1：創建一個students數據庫，以及表的創建，查找等功能的練習；
1.1.創建一個students數據庫
mysql> CREATE DATABASE IF NOT EXISTS students CHARACTER SET 'gbk' COLLATE 'gbk_chinese_ci';
#字符集為gbk，排序規則為gbk_chinese_ci
Query OK, 1 row affected (0.01 sec)
mysql> USE students;
Database changed
mysql> CREATE TABLE courses(CID TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,Couse VARCHAR(50) NOT NULL);
Query OK, 0 rows affected (0.07 sec)
mysql> SHOW TABLE STATUS LIKE 'courses'\G;
************************ 1. row ***********************
Name: courses
Engine: InnoDB #數據庫引擎
Version: 10
Row_format: Compact #類似壓縮格式存儲
Rows: 0
Avg_row_length: 0
Data_length: 16384
...
1.2.刪除表，新建引擎為MyISAM的新表
mysql> DROP TABLES courses; #刪除表
Query OK, 0 rows affected (0.01 sec)
mysql> CREATE TABLE courses(CID TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,Couse VARCHAR(50) NOT NULL) ENGINE=MyISAM; #ENGINE設定引擎為MyISAM
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW TABLE STATUS LIKE 'courses' \G;
*************** 1. row *************
Name: courses
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 0
Max_data_length: 281474976710655
...
1 row in set (0.00 sec)
1.3.1新表中加入值
mysql> INSERT INTO courses (Couse) values ('physics'),('english'),('chemistry'),('maths');
#插入Couse課程字段數據，添加物理，英語，化學，數學等課程。
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM courses; #查詢courses表的條目
+-----+-----------+
| CID | Couse |
+-----+-----------+
| 1 | physics |
| 2 | english |
| 3 | chemistry|
| 4 | maths |
+-----+-----------+
4 rows in set (0.00 sec)
mysql> SHOW INDEXES FROM courses; #查看courses表的索引 -B樹索引
+---------+------------+----------+--------------+
| Table| Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+----------+--------------+
| courses | 0 | PRIMARY | 1 | CID | A | 4 | NULL | NULL | | BTREE | | |
1 row in set (0.00 sec)
1.3.2新表中加入查詢值，但生成的表與原表格式會不一致，可先創建表再插入值；
mysql> CREATE TABLE testcourses SELECT * FROM courses WHERE CID <= 2;
#查找courses表中CID字段小于等于2的數據，并把查找到的數據作為新建testcourses表的數據內容。
Query OK, 2 rows affected (0.08 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> SHOW TABLES; #查看當前數據庫表的信息
+--------------------+
| Tables_in_students |
+--------------------+
| courses |
| testcourses |
+--------------------+
2 rows in set (0.00 sec)
mysql> SELECT * FROM testcourses; #查看testcourses表的內容
+-----+---------+
| CID | Couse |
+-----+---------+
| 1 | physics |
| 2 | english |
+-----+---------+
2 rows in set (0.00 sec)
mysql> DESC courses; #查看courses表結構
+-------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------------+
| CID | tinyint(3) unsigned | NO | PRI | NULL| auto_increment |
| Couse | varchar(50) | NO | | NULL | |
2 rows in set (0.00 sec)
mysql> DESC testcourses; #查看testcourses表結構與上面的courses不一樣
+-------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------------+
| CID | tinyint(3) unsigned | NO | | 0 | |
| Couse | varchar(50) | NO | | NULL | |
+-------+---------------------+
2 rows in set (0.00 sec)
mysql> CREATE TABLE test LIKE courses; #以courses表為模板創建test空表。
Query OK, 0 rows affected (0.00 sec)
mysql> DESC test; #查看test表結構
+-------+---------------------+------+-----+---------+----------------+
| Field | Type| Null | Key | Default | Extra |
+-------+---------------------+
| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |
| Couse | varchar(50) | NO | | NULL | |
2 rows in set (0.00 sec)
mysql> SHOW TABLE STATUS LIKE 'test'\G; #查看test表的狀態
*************** 1. row *********
Name: test
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 0
Max_data_length: 281474976710655
Index_length: 1024
Data_free: 0
Auto_increment: 1
Create_time: 2017-04-25 11:31:46
Update_time: 2017-04-25 11:31:46
Check_time: NULL
Collation: gbk_chinese_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
實例2.建立student表，并進行相關數據的插入，查詢操作練習，修改引擎，修改字段修飾，增加外鍵索引；
2.1.建立student表
mysql>CREATE TABLE student (SID INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,Name VARCHAR(30),CID INT NOT NULL);
#創建student表，包含3個字段，SID字段 為無符號、非空、自動增長、主鍵的整數型，
Name字段 為變長30字符，
CID字符 為非空整數型。
mysql> SHOW TABLES;
+--------------------+
| Tables_in_students |
+--------------------+
| courses |
| student |
| testcourses |
3 rows in set (0.00 sec)
2.2.在student表中插入數據
mysql>INSERT INTO student (Name,CID) VALUES ('Li Li',1),('ChengChen',2); #對Name,CID字段插入2條數據。
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql>SELECT * FROM student; #查詢student表
+-----+------------+-----+
| SID | Name | CID |
+-----+------------+-----+
| 1 | Li Li | 1 |
| 2 | ChengChen | 2 |
2 rows in set (0.00 sec)
2.3.在student表中查詢數據
mysql> SELECT * FROM courses; #查詢courses表
+-----+-----+
| CID| Couse|
+-----+-----+
|1|physics|
|2|english|
|3|chemistry|
|4| maths|
|5| Hamagong|
|6| Pixiejianfa|
|7| Kuihuabaodian |
7 rows in set (0.00 sec)
mysql> SELECT Name,Couse FROM student,courses WHERE student.CID=courses.CID; #查詢student表和courses表中CID相同的Name和Couse字段內容
+-----+------+
| Name|Couse|
+------+-----+
| Li Li| physics |
| Cheng Chen | english |
2 rows in set (0.00 sec)
2.4.在student表中刪除、修改數據
mysql>DELETE FROM courses WHERE CID > 5; #刪除SID大于5的行。
Query OK, 5 rows affected (0.01 sec)
mysql>ALTER TABLE courses ENGINE=Innodb; #修改courses表的引擎為Innodb;
Query OK, 4 rows affected (0.03 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql>ALTER TABLE student MODIFY CID TINYINT UNSIGNED NOT NULL;#修改student表中CID字段的修飾MODIFY
Query OK, 4 rows affected (0.02 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> DESC courses;
+-----+--------+------+-----+---------+-----------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+
| CID | tinyint(3) unsigned | NO | PRI |NULL | auto_increment |
| Couse | varchar(50) | NO | | NULL | |
2 rows in set (0.00 sec)
mysql> DESC student;
+-------+--------+------+-----+---------+-----------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+
| SID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(30)| YES | | NULL | |
| CID | tinyint(3) unsigned | NO | | NULL | |
3 rows in set (0.00 sec)
mysql> ALTER TABLE student ADD FOREIGN KEY foreign_cid (CID) REFERENCES courses (CID);
#為student表的CID字段增加一個外鍵foreign_cid關聯courses表的CID字段。
Query OK, 4 rows affected (0.03 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> SHOW INDEXES FROM student; #查看student表的索引
+---------+------------+----------+-----------+----------+---------+----------+
|Table|Non_unique|Key_name|Seq_in_index|Column_name|Collation|Cardinality|Sub_part| Packed| Null| Index_type| Comment| Index_comment|
+---------+------------+------------+
|student |0 | PRIMARY | 1 | SID | A|2 |NULL | NULL| | BTREE| | |
|student |1 |foreign_cid| 1 | CID | A|2 |NULL | NULL| | BTREE| | |
2 rows in set (0.00 sec)
mysql> INSERT INTO student (Name,CID) VALUES ('Guo Xiang',5);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`students`.`student`, CONSTRAINT `student_ibfk_1` FOREIGN KEY (`CID`) REFERENCES `courses` (`CID`))
#提示報錯，由于CID外鍵索引courses表中CID沒有5，所以無法增加。
mysql> ALTER TABLE student AUTO_INCREMENT=5; #設定student表下一條數據的自動增長主鍵SID從5開始增長。
Query OK, 4 rows affected (0.05 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM student; #查詢表的內容
+-----+----------+-----+
| SID | Name| CID |
+-----+--------+-----+
| 1 | Li Lianjie | 1 |
| 2 | Cheng Long | 2 |
| 3 | Xiao Longnv | 3 |
| 4 | Yang Guo | 4 |
4 rows in set (0.00 sec)
mysql> INSERT INTO student (Name,CID) VALUES ('Guo Xiang',3);
#插入一條數據，SID主鍵由于上面設置從5開始增長，所以剛插入的數據是從5開始；
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM student;
+-----+----------+-----+
| SID | Name | CID |
+-----+-------------+-----+
| 1 | Li Lianjie| 1 |
| 2 | Cheng Long | 2 |
| 3 | Xiao Longnv | 3 |
| 4 | Yang Guo | 4 |
|5 | Guo Xiang | 3 |
5 rows in set (0.00 sec)
mysql> INSERT INTO student (Name,CID) VALUES ('Qiao Feng',2);插入數據
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM student;
mysql> DELETE FROM student WHERE SID >2 AND SID <5; #刪除2<SID<5的行
Query OK, 2 rows affected (0.00 sec)
mysql> SELECT * FROM student; #驗證
+-----+------------+-----+
| SID | Name | CID |
| 1 | Li Lianjie | 1 |
| 2 | Cheng Long | 2 |
| 5 | Guo Xiang | 3 |
| 6 | Qiao Feng | 2 |
4 rows in set (0.00 sec)
mysql> DELETE FROM student WHERE SID in (5,6); #刪除SID為5和6的行
Query OK, 2 rows affected (0.00 sec)
mysql> SELECT * FROM student;
+-----+------------+-----+
| SID | Name | CID |
+-----+------------+-----+
| 1 | Li Lianjie | 1 |
| 2 | Cheng Long | 2 |
2 rows in set (0.00 sec)
mysql>ALTER TABLE student AUTO_INCREMENT=3;#設定表下一條數據的自動增長主鍵SID從3開始增長
Query OK, 2 rows affected (0.07 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql>INSERT INTO student (Name,CID) VALUES ('Yang Guo',3),('Guo Jing',4);#插入2條數據
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM student;
+-----+------------+-----+
| SID | Name | CID |
+-----+------------+-----+
| 1 | Li Lianjie | 1 |
| 2 | Cheng Long | 2 |
| 3 | Yang Guo | 3 |
| 4 | Guo Jing | 4 |
4 rows in set (0.00 sec)
2.5.在student表中創建索引，實現比較或排序
mysql> SELECT * FROM student;
+-----+------------+-----+
| SID | Name | CID |
+-----+------------+-----+
| 1 | Li Li | 1 |
| 2 | Cheng Chen | 2 |
| 3 | YangGuo | 3 |
| 4 | GuoJing | 4 |
4 rows in set (0.00 sec)
mysql> CREATE INDEX name_on_student ON student (Name) USING BTREE;
Query OK, 0 rows affected (0.09 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> DROP INDEX name_on_student ON student; #索引只能新建或刪除,因其是結構無法修改
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> CREATE INDEX name_on_student ON student (Name(5) DESC) USING BTREE;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW INDEXES FROM student;
+---------+------------+-----------------+--------------+-------------+-----------+
| Table| Non_unique| Key_name| Seq_in_index| Column_name| Collation| Cardinality| Sub_part | Packed | Null| Index_type| Comment| Index_comment |
+---------+------------+-----------------+
| student|0 | PRIMARY| 1 | SID | A | 2 | NULL | NULL | BTREE | | |
| student|1 | foreign_cid | 1| CID | A |2 | NULL | NULL| | BTREE | | |
| student|1 | name_on_student|1| Name| A |4 | 5 | NULL | YES| BTREE | | |
3 rows in set (0.00 sec)
---end-6---
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