數據庫環境準備:
創建數據庫
create database mysql_demo1 charset=utf8;
MariaDB [(none)]> create database mysql_demo1 charset=utf8;
Query OK, 1 row affected (0.00 sec)
使用數據庫
use mysql_demo1;
MariaDB [(none)]> use mysql_demo1;
Database changed
創建表參數
unsigned 整型無符號
signed 整型有符號
primary key 詳解參考:http://c.biancheng.net/view/2440.html
foreign key 詳解參考:http://c.biancheng.net/view/2441.html
unique key 詳解參考:http://c.biancheng.net/view/2445.html
auto_increment 自增字段
not null 不爲空
default 默認值
int int類型
char 存儲字符串
varchar 存儲字符串（char是屬於固定長度的字符類型，而varchar是屬於可變長度的字符類型。）
tinyint 型的字段如果不設置UNSIGNED類型,存儲-128到127的整數。 （tinyint(1)，tinyint(２),tinyint(3),tinyint(4)）(稍後詳解)
DECIMAL (5,2)規定了存儲的值將不會超過5位數字，開且小數點後面有2位數字。
enum 枚舉類型 添加新的數據不爲這四個值則會報錯
bit 利用它可定義一個位變量，但不能定義位指針，也不能定義位數組。它的值是一個二進制位，不是0就是1，類似Boolean類型中的True和False。
創建students表
create table students(
id int unsigned primary key auto_increment not null,
name varchar(20) default '',
age tinyint unsigned default 0,
height decimal(5,2),
gender enum('男','女','中性','保密') default '保密',
cls_id int unsigned default 0,
is_delete bit default 0
);
MariaDB [mysql_demo1]> create table students(
-> id int unsigned primary key auto_increment not null,
-> name varchar(20) default '',
-> age tinyint unsigned default 0,
-> height decimal(5,2),
-> gender enum('男','女','中性','保密') default '保密',
-> cls_id int unsigned default 0,
-> is_delete bit default 0
-> );
Query OK, 0 rows affected (0.01 sec)
創建classes表
create table classes(
id int unsigned auto_increment primary key not null,
name varchar(30) not null
);
MariaDB [mysql_demo1]> create table classes(
-> id int unsigned auto_increment primary key not null,
-> name varchar(30) not null
-> );
Query OK, 0 rows affected (0.00 sec)
查看錶是否創建成功
show tables;
MariaDB [mysql_demo1]> show tables;
+-----------------------+
| Tables_in_mysql_demo1 |
+-----------------------+
| classes |
| students |
+-----------------------+
2 rows in set (0.00 sec)
準備數據:
向students表中插入數據
insert into students values
(0,‘小明’,18,180.00,1,1,0),
(0,‘小張’,18,160.00,1,2,0),
(0,‘小紅’,20,170.00,2,1,0),
(0,‘周杰’,38,175.00,1,1,0),
(0,‘彭玉宴’,56,150.00,1,2,0),
(0,‘劉德化’,29,150.00,1,2,0),
(0,‘張學友’,36,180.00,1,1,0),
(0,‘周杰倫’,25,166.00,1,1,0),
(0,‘風姐’,16,169.00,2,1,0),
(0,‘王小明’,57,162.00,1,2,1),
(0,‘張小華’,46,173.00,2,1,0),
(0,‘金星’,29,175.00,2,1,1),
(0,‘黃蓉’,66,185.00,3,2,0),
(0,‘古天樂’,15,186.00,4,2,0),
(0,‘劉小海’,31,175.00,4,1,0),
(0,‘小月月’,57,163.00,2,1,0);
MariaDB [mysql_demo1]> insert into students values
-> (0,'小明',18,180.00,1,1,0),
-> (0,'小張',18,160.00,1,2,0),
-> (0,'小紅',20,170.00,2,1,0),
-> (0,'周杰',38,175.00,1,1,0),
-> (0,'彭玉宴',56,150.00,1,2,0),
-> (0,'劉德化',29,150.00,1,2,0),
-> (0,'張學友',36,180.00,1,1,0),
-> (0,'周杰倫',25,166.00,1,1,0),
-> (0,'風姐',16,169.00,2,1,0),
-> (0,'王小明',57,162.00,1,2,1),
-> (0,'張小華',46,173.00,2,1,0),
-> (0,'金星',29,175.00,2,1,1),
-> (0,'黃蓉',66,185.00,3,2,0),
-> (0,'古天樂',15,186.00,4,2,0),
-> (0,'劉小海',31,175.00,4,1,0),
-> (0,'小月月',57,163.00,2,1,0);
Query OK, 16 rows affected (0.00 sec)
Records: 16 Duplicates: 0 Warnings: 0
向classes表插入數據
insert into classes values
(0, “python_01期”),
(0, “python_02期”);
MariaDB [mysql_demo1]> insert into classes values
-> (0, "python_01期"),
-> (0, "python_02期");
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
查詢所有字段
select * from 表名; (也驗證一下上面數據是否插入成功)
select * from students;
select * from classes;
MariaDB [mysql_demo1]> select * from students;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 1 | 小明 | 18 | 180.00 | 男 | 1 | |
| 2 | 小張 | 18 | 160.00 | 男 | 2 | |
| 3 | 小紅 | 20 | 170.00 | 女 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 5 | 彭玉宴 | 56 | 150.00 | 男 | 2 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 9 | 風姐 | 16 | 169.00 | 女 | 1 | |
| 10 | 王小明 | 57 | 162.00 | 男 | 2 | |
| 11 | 張小華 | 46 | 173.00 | 女 | 1 | |
| 12 | 金星 | 29 | 175.00 | 女 | 1 | |
| 13 | 黃蓉 | 66 | 185.00 | 中性 | 2 | |
| 14 | 古天樂 | 15 | 186.00 | 保密 | 2 | |
| 15 | 劉小海 | 31 | 175.00 | 保密 | 1 | |
| 16 | 小月月 | 57 | 163.00 | 女 | 1 | |
+----+-----------+------+--------+--------+--------+-----------+
16 rows in set (0.00 sec)
MariaDB [mysql_demo1]> select * from classes;
+----+--------------+
| id | name |
+----+--------------+
| 1 | python_01期 |
| 2 | python_02期 |
+----+--------------+
2 rows in set (0.00 sec)
查詢指定字段
select 列1,列2,… from 表名;
select name,age from students;
MariaDB [mysql_demo1]> select name,age from students;
+-----------+------+
| name | age |
+-----------+------+
| 小明 | 18 |
| 小張 | 18 |
| 小紅 | 20 |
| 周杰 | 38 |
| 彭玉宴 | 56 |
| 劉德化 | 29 |
| 張學友 | 36 |
| 周杰倫 | 25 |
| 風姐 | 16 |
| 王小明 | 57 |
| 張小華 | 46 |
| 金星 | 29 |
| 黃蓉 | 66 |
| 古天樂 | 15 |
| 劉小海 | 31 |
| 小月月 | 57 |
+-----------+------+
16 rows in set (0.00 sec)
使用 as 給字段起別名 作用於當前語句
select 字段 as 名字… from 表名;
select name as 名字,age as 年齡 from students;
MariaDB [mysql_demo1]> select name as 名字,age as 年齡 from students;
+-----------+-------------+
| 名字 | as 年齡 |
+-----------+-------------+
| 小明 | 18 |
| 小張 | 18 |
| 小紅 | 20 |
| 周杰 | 38 |
| 彭玉宴 | 56 |
| 劉德化 | 29 |
| 張學友 | 36 |
| 周杰倫 | 25 |
| 風姐 | 16 |
| 王小明 | 57 |
| 張小華 | 46 |
| 金星 | 29 |
| 黃蓉 | 66 |
| 古天樂 | 15 |
| 劉小海 | 31 |
| 小月月 | 57 |
+-----------+-------------+
16 rows in set (0.00 sec)
使用 as 給表名起別名 作用於當前語句
select 表別名.字段1,表別名.字段2 from 表 as 表別名;
select s.name,s.age from students as s;
MariaDB [mysql_demo1]> select s.name,s.age from students as s;
+-----------+------+
| name | age |
+-----------+------+
| 小明 | 18 |
| 小張 | 18 |
| 小紅 | 20 |
| 周杰 | 38 |
| 彭玉宴 | 56 |
| 劉德化 | 29 |
| 張學友 | 36 |
| 周杰倫 | 25 |
| 風姐 | 16 |
| 王小明 | 57 |
| 張小華 | 46 |
| 金星 | 29 |
| 黃蓉 | 66 |
| 古天樂 | 15 |
| 劉小海 | 31 |
| 小月月 | 57 |
+-----------+------+
16 rows in set (0.00 sec)
跨表查詢 這種查不準不常用
select students.name,classes.name from students,classes;
MariaDB [mysql_demo1]> select students.name,classes.name from students,classes;
+-----------+--------------+
| name | name |
+-----------+--------------+
| 小明 | python_01期 |
| 小明 | python_02期 |
| 小張 | python_01期 |
| 小張 | python_02期 |
| 小紅 | python_01期 |
| 小紅 | python_02期 |
| 周杰 | python_01期 |
| 周杰 | python_02期 |
| 彭玉宴 | python_01期 |
| 彭玉宴 | python_02期 |
| 劉德化 | python_01期 |
| 劉德化 | python_02期 |
| 張學友 | python_01期 |
| 張學友 | python_02期 |
| 周杰倫 | python_01期 |
| 周杰倫 | python_02期 |
| 風姐 | python_01期 |
| 風姐 | python_02期 |
| 王小明 | python_01期 |
| 王小明 | python_02期 |
| 張小華 | python_01期 |
| 張小華 | python_02期 |
| 金星 | python_01期 |
| 金星 | python_02期 |
| 黃蓉 | python_01期 |
| 黃蓉 | python_02期 |
| 古天樂 | python_01期 |
| 古天樂 | python_02期 |
| 劉小海 | python_01期 |
| 劉小海 | python_02期 |
| 小月月 | python_01期 |
| 小月月 | python_02期 |
+-----------+--------------+
32 rows in set (0.00 sec)
distinct 消除重複行 也就是指定列的不重複的值
以students爲例 裏面有四個性別 我們查詢出來
select distinct gender from students;
MariaDB [mysql_demo1]> select distinct gender from students;
+--------+
| gender |
+--------+
| 男 |
| 女 |
| 中性 |
| 保密 |
+--------+
4 rows in set (0.00 sec)
如果distinct後有多個字段, 只有當查詢的多列的查詢結果完全相同才能去重
查詢age 大於18歲的所有數據
select * from students where age > 18;
MariaDB [mysql_demo1]> select * from students where age > 18;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 3 | 小紅 | 20 | 170.00 | 女 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 5 | 彭玉宴 | 56 | 150.00 | 男 | 2 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 10 | 王小明 | 57 | 162.00 | 男 | 2 | |
| 11 | 張小華 | 46 | 173.00 | 女 | 1 | |
| 12 | 金星 | 29 | 175.00 | 女 | 1 | |
| 13 | 黃蓉 | 66 | 185.00 | 中性 | 2 | |
| 15 | 劉小海 | 31 | 175.00 | 保密 | 1 | |
| 16 | 小月月 | 57 | 163.00 | 女 | 1 | |
+----+-----------+------+--------+--------+--------+-----------+
查詢age 大於18 小於40的所有數據 有兩種方法
select * from students where age > 18 and age < 40;
select * from students where age between 18 and 40;
注意兩種不同之處 between是並等於條件
MariaDB [mysql_demo1]> select * from students where age > 18 and age < 40;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 3 | 小紅 | 20 | 170.00 | 女 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 12 | 金星 | 29 | 175.00 | 女 | 1 | |
| 15 | 劉小海 | 31 | 175.00 | 保密 | 1 | |
+----+-----------+------+--------+--------+--------+-----------+
7 rows in set (0.00 sec)
MariaDB [mysql_demo1]> select * from students where age between 18 and 40;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 1 | 小明 | 18 | 180.00 | 男 | 1 | |
| 2 | 小張 | 18 | 160.00 | 男 | 2 | |
| 3 | 小紅 | 20 | 170.00 | 女 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 12 | 金星 | 29 | 175.00 | 女 | 1 | |
| 15 | 劉小海 | 31 | 175.00 | 保密 | 1 | |
+----+-----------+------+--------+--------+--------+-----------+
9 rows in set (0.00 sec)
查詢age 大於18小於40的所有女性的數據
select * from students where age between 18 and 40 and gender=‘女’;
MariaDB [mysql_demo1]> select * from students where age between 18 and 40 and gender='女';
+----+--------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+--------+------+--------+--------+--------+-----------+
| 3 | 小紅 | 20 | 170.00 | 女 | 1 | |
| 12 | 金星 | 29 | 175.00 | 女 | 1 | |
+----+--------+------+--------+--------+--------+-----------+
2 rows in set (0.00 sec)
order by 排序 asc正序 desc倒序 查詢男性身高從高到底查詢
select * from students where gender=‘男’ order by height desc;
MariaDB [mysql_demo1]> select * from students where gender='男' order by height desc;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 1 | 小明 | 18 | 180.00 | 男 | 1 | |
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 10 | 王小明 | 57 | 162.00 | 男 | 2 | |
| 2 | 小張 | 18 | 160.00 | 男 | 2 | |
| 5 | 彭玉宴 | 56 | 150.00 | 男 | 2 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
+----+-----------+------+--------+--------+--------+-----------+
8 rows in set (0.00 sec)
查詢男性身高從高到底查詢 如果身高一樣則年齡從高到底來顯示 依次類推
select * from students where gender=‘男’ order by height desc,age desc;
MariaDB [mysql_demo1]> select * from students where gender='男' order by height desc,age desc;
+----+-----------+------+--------+--------+--------+-----------+
| id | name | age | height | gender | cls_id | is_delete |
+----+-----------+------+--------+--------+--------+-----------+
| 7 | 張學友 | 36 | 180.00 | 男 | 1 | |
| 1 | 小明 | 18 | 180.00 | 男 | 1 | |
| 4 | 周杰 | 38 | 175.00 | 男 | 1 | |
| 8 | 周杰倫 | 25 | 166.00 | 男 | 1 | |
| 10 | 王小明 | 57 | 162.00 | 男 | 2 | |
| 2 | 小張 | 18 | 160.00 | 男 | 2 | |
| 5 | 彭玉宴 | 56 | 150.00 | 男 | 2 | |
| 6 | 劉德化 | 29 | 150.00 | 男 | 2 | |
+----+-----------+------+--------+--------+--------+-----------+
8 rows in set (0.01 sec)