MySQL 【进阶查询】

# mysql> select bName,price from books where price  in (50,60,70) order by price asc;  
+--------------------------------------+-------+  
| bName                          | price |  
+--------------------------------------+-------+  
| Illustrator 10完全手册      |    50 |  
| FreeHand 10基础教程      |    50 |  
| 网站设计全程教程             |    50 |  
| ASP数据库系统开发实例导航  |    60 |  
| Delphi 5程序设计与控件参考  |    60 |  
| ASP数据库系统开发实例导航   |    60 |  

# mysql> select bName,price from books where price  in (50,60,70) order by price desc;  
+--------------------------------+-----------------+  
| bName                                | price |  
+--------------------------------+-----------------+  
| ASP数据库系统开发实例导航     |    60 |  
| Delphi 5程序设计与控件参考    |    60 |  
| ASP数据库系统开发实例导航    |    60 |  
| Illustrator 10完全手册           |    50 |  
| FreeHand 10基础教程           |    50 |  
| 网站设计全程教程                  |    50 |  

select bName,price from books where price  in (50,60,70) order by price desc,bName desc; 

inner join ... on
select ... from 表A inner join 表B;
select * from students inner join classes;

# 查询 有能够对应班级的学生以及班级信息
select * from students inner join classes on students.cls_id = classes.id;

# 按照要求显示姓名、班级
select students.name,classes.name from students inner join classes on students.cls_id = classes.id;

# 给数据表起名字
select s.name,c.name from students as s inner join classes as c on s.cls_id = c.id;

# 查询 有能够对应班级的学生以及班级信息，显示学生的所有信息 students.*，只显示班级名称 classes.name.
select s.*,c.name from students as s inner join classes as c on s.cls_id = c.id;

# 在以上的查询中，将班级姓名显示在第1列
select c.name,s.* from students as s inner join classes as c on s.cls_id = c.id;

# 查询 有能够对应班级的学生以及班级信息, 按照班级进行排序
select c.xxx s.xxx from students as s inner join clssses as c on .... order by ....;
select c.name,s.* from students as s inner join classes as c on s.cls_id = c.id order by c.name;

# 当时同一个班级的时候，按照学生的id进行从小到大排序
select c.name,s.* from students as s inner join classes as c on s.cls_id = c.id order by c.name,id asc;

# left join
# 查询每位学生对应的班级信息
select * from students left join classes on students.cls_id = classes.id;

# right join
select * from students right join classes on students.cls_id = classes.id;

# 查询没有对应班级信息的学生
# 语句
select ... from xxx as s left join xxx as c on..... where .....
select ... from xxx as s left join xxx as c on..... having .....

# 列
select * from students left join classes on students.cls_id = classes.id where classes.name is null;
#(注意)不建议使用 select * from students left join classes on students.cls_id=classes.id having classes.id is null;
# right join   on
# 将数据表名字互换位置，用left join完成

应用示例

# mysql> use RUNOOB;
Database changed
# mysql> CREATE TABLE runoob_transaction_test( id int(5)) engine=innodb;  # 创建数据表
Query OK, 0 rows affected (0.04 sec)
 
# mysql> select * from runoob_transaction_test;
Empty set (0.01 sec)
 
# mysql> begin;  # 开始事务
Query OK, 0 rows affected (0.00 sec)
 
# mysql> insert into runoob_transaction_test value(5);
Query OK, 1 rows affected (0.01 sec)
 
# mysql> insert into runoob_transaction_test value(6);
Query OK, 1 rows affected (0.00 sec)
 
# mysql> commit; # 提交事务
Query OK, 0 rows affected (0.01 sec)
 
# mysql>  select * from runoob_transaction_test;
+------+
| id   |
+------+
| 5    |
| 6    |
+------+
rows in set (0.01 sec)
 
# mysql> begin;    # 开始事务
Query OK, 0 rows affected (0.00 sec)
 
# mysql>  insert into runoob_transaction_test values(7);
Query OK, 1 rows affected (0.00 sec)
 
# mysql> rollback;   # 回滚
Query OK, 0 rows affected (0.00 sec)
 
# mysql>   select * from runoob_transaction_test;   # 因为回滚所以数据没有插入
+------+
| id   |
+------+
| 5    |
| 6    |
+------+
rows in set (0.01 sec)
 
# mysql>

事物测试

<?php
$dbhost = ‘localhost:3306‘;  // mysql服务器主机地址
$dbuser = ‘root‘;            // mysql用户名
$dbpass = ‘123456‘;          // mysql用户名密码
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
    die(‘连接失败: ‘ . mysqli_error($conn));
}
// 设置编码，防止中文乱码
mysqli_query($conn, "set names utf8");
mysqli_select_db( $conn, ‘RUNOOB‘ );
mysqli_query($conn, "SET AUTOCOMMIT=0"); // 设置为不自动提交，因为MYSQL默认立即执行
mysqli_begin_transaction($conn);            // 开始事务定义
 
if(!mysqli_query($conn, "insert into runoob_transaction_test (id) values(8)"))
{
    mysqli_query($conn, "ROLLBACK");     // 判断当执行失败时回滚
}
 
if(!mysqli_query($conn, "insert into runoob_transaction_test (id) values(9)"))
{
    mysqli_query($conn, "ROLLBACK");      // 判断执行失败时回滚
}
mysqli_commit($conn);            //执行事务
mysqli_close($conn);
?>

PHP中使用事物示例

# mysql> ALTER TABLE testalter_tbl ALTER i SET DEFAULT 1000;
# mysql> SHOW COLUMNS FROM testalter_tbl;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| c     | char(1) | YES  |     | NULL    |       |
| i     | int(11) | YES  |     | 1000    |       |
+-------+---------+------+-----+---------+-------+
rows in set (0.00 sec)

# mysql> ALTER TABLE testalter_tbl ALTER i DROP DEFAULT;
# mysql> SHOW COLUMNS FROM testalter_tbl;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| c     | char(1) | YES  |     | NULL    |       |
| i     | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
rows in set (0.00 sec)
Changing a Table Type:

mysql> CREATE TEMPORARY TABLE SalesSummary (
    -> product_name VARCHAR(50) NOT NULL
    -> , total_sales DECIMAL(12,2) NOT NULL DEFAULT 0.00
    -> , avg_unit_price DECIMAL(7,2) NOT NULL DEFAULT 0.00
    -> , total_units_sold INT UNSIGNED NOT NULL DEFAULT 0
);
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO SalesSummary
    -> (product_name, total_sales, avg_unit_price, total_units_sold)
    -> VALUES
    -> (‘cucumber‘, 100.25, 90, 2);

mysql> SELECT * FROM SalesSummary;
+--------------+-------------+----------------+------------------+
| product_name | total_sales | avg_unit_price | total_units_sold |
+--------------+-------------+----------------+------------------+
| cucumber     |      100.25 |          90.00 |                2 |
+--------------+-------------+----------------+------------------+
row in set (0.00 sec)

mysql> CREATE TEMPORARY TABLE SalesSummary (
    -> product_name VARCHAR(50) NOT NULL
    -> , total_sales DECIMAL(12,2) NOT NULL DEFAULT 0.00
    -> , avg_unit_price DECIMAL(7,2) NOT NULL DEFAULT 0.00
    -> , total_units_sold INT UNSIGNED NOT NULL DEFAULT 0
);
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO SalesSummary
    -> (product_name, total_sales, avg_unit_price, total_units_sold)
    -> VALUES
    -> (‘cucumber‘, 100.25, 90, 2);

mysql> SELECT * FROM SalesSummary;
+--------------+-------------+----------------+------------------+
| product_name | total_sales | avg_unit_price | total_units_sold |
+--------------+-------------+----------------+------------------+
| cucumber     |      100.25 |          90.00 |                2 |
+--------------+-------------+----------------+------------------+
row in set (0.00 sec)
mysql> DROP TABLE SalesSummary;
mysql>  SELECT * FROM SalesSummary;
ERROR 1146: Table ‘RUNOOB.SalesSummary‘ doesn‘t exist

# mysql> SHOW CREATE TABLE runoob_tbl \G;
*************************** 1. row ***************************
       Table: runoob_tbl
Create Table: CREATE TABLE `runoob_tbl` (
  `runoob_id` int(11) NOT NULL auto_increment,
  `runoob_title` varchar(100) NOT NULL default ‘‘,
  `runoob_author` varchar(40) NOT NULL default ‘‘,
  `submission_date` date default NULL,
  PRIMARY KEY  (`runoob_id`),
  UNIQUE KEY `AUTHOR_INDEX` (`runoob_author`)
) ENGINE=InnoDB 
row in set (0.00 sec)

ERROR:
No query specified

# mysql> CREATE TABLE `clone_tbl` (
  -> `runoob_id` int(11) NOT NULL auto_increment,
  -> `runoob_title` varchar(100) NOT NULL default ‘‘,
  -> `runoob_author` varchar(40) NOT NULL default ‘‘,
  -> `submission_date` date default NULL,
  -> PRIMARY KEY  (`runoob_id`),
  -> UNIQUE KEY `AUTHOR_INDEX` (`runoob_author`)
-> ) ENGINE=InnoDB;
Query OK, 0 rows affected (1.80 sec)

# 执行完第二步骤后，你将在数据库中创建新的克隆表 clone_tbl。 如果你想拷贝数据表的数据你可以使用 INSERT INTO... SELECT 语句来实现。

mysql> INSERT INTO clone_tbl (runoob_id,
    ->                        runoob_title,
    ->                        runoob_author,
    ->                        submission_date)
    -> SELECT runoob_id,runoob_title,
    ->        runoob_author,submission_date
    -> FROM runoob_tbl;
Query OK, 3 rows affected (0.07 sec)
Records: 3  Duplicates: 0  Warnings: 0

# 执行以上步骤后，你将完整的复制表，包括表结构及表数据。

# 使用 mysql_insertid 属性来获取 AUTO_INCREMENT 的值。 实例如下：

$dbh->do ("INSERT INTO insect (name,date,origin)
VALUES(‘moth‘,‘2001-09-14‘,‘windowsill‘)");
my $seq = $dbh->{mysql_insertid};

PHP 通过 mysql_insert_id ()函数来获取执行的插入SQL语句中 AUTO_INCREMENT列的值。

mysql_query ("INSERT INTO insect (name,date,origin)
VALUES(‘moth‘,‘2001-09-14‘,‘windowsill‘)", $conn_id);
$seq = mysql_insert_id ($conn_id);

$ mysqldump -u root -p RUNOOB runoob_tbl > dump.txt
password ******
以上命令创建的文件内容如下：

-- MySQL dump 8.23
--
-- Host: localhost    Database: RUNOOB
---------------------------------------------------------
-- Server version       3.23.58

--
-- Table structure for table `runoob_tbl`
--

CREATE TABLE runoob_tbl (
  runoob_id int(11) NOT NULL auto_increment,
  runoob_title varchar(100) NOT NULL default ‘‘,
  runoob_author varchar(40) NOT NULL default ‘‘,
  submission_date date default NULL,
  PRIMARY KEY  (runoob_id),
  UNIQUE KEY AUTHOR_INDEX (runoob_author)
) TYPE=MyISAM;

--
-- Dumping data for table `runoob_tbl`
--

INSERT INTO runoob_tbl 
       VALUES (1,‘Learn PHP‘,‘John Poul‘,‘2007-05-24‘);
INSERT INTO runoob_tbl 
       VALUES (2,‘Learn MySQL‘,‘Abdul S‘,‘2007-05-24‘);
INSERT INTO runoob_tbl 
       VALUES (3,‘JAVA Tutorial‘,‘Sanjay‘,‘2007-05-06‘);

# 如果你需要导出整个数据库的数据，可以使用以下命令：
$ mysqldump -u root -p RUNOOB > database_dump.txt
password ******

# 如果需要备份所有数据库，可以使用以下命令：
$ mysqldump -u root -p --all-databases > database_dump.txt
password ******
--all-databases 选项在 MySQL 3.23.12 及以后版本加入。
# 该方法可用于实现数据库的备份策略。

# 如果你需要将数据拷贝至其他的 MySQL 服务器上, 你可以mysqldump 命令中指定数据库名及数据表。

# 在源主机上执行以下命令，将数据备份至 dump.txt 文件中:
$ mysqldump -u root -p database_name table_name > dump.txt
password *****

#如果完整备份数据库，则无需使用特定的表名称。
# 如果你需要将备份的数据库导入到MySQL服务器中，可以使用以下命令，使用以下命令你需要确认数据库已经创建：
$ mysql -u root -p database_name < dump.txt
password *****

# 你也可以使用以下命令将导出的数据直接导入到远程的服务器上，但请确保两台服务器是相通的，是可以相互访问的：
$ mysqldump -u root -p database_name        | mysql -h other-host.com database_name
# 以上命令中使用了管道来将导出的数据导入到指定的远程主机上。

# mysql> select 2=3;
+-----+
| 2=3 |
+-----+
|   0 |
+-----+
# mysql> select NULL = NULL;
+-------------+
| NULL = NULL |
+-------------+
|        NULL |
+-------------+

# mysql> select 2<>3;
+------+
| 2<>3 |
+------+
|    1 |
+------+

# 与 = 的区别在于当两个操作码均为 NULL 时，其所得值为 1 而不为 NULL，而当一个操作码为 NULL 时，其所得值为 0而不为 NULL。
# mysql> select 2<=>3;
+-------+
| 2<=>3 |
+-------+
|     0 |
+-------+
# mysql> select null=null;
+-----------+
| null=null |
+-----------+
|      NULL |
+-----------+      
# mysql> select null<=>null;
+-------------+
| null<=>null |
+-------------+
|           1 |
+-------------+

# mysql> select 2<3;
+-----+
| 2<3 |
+-----+
|   1   |
+-----+

# mysql> select 2<=3;
+------+
| 2<=3 |
+------+
|    1   |
+------+

# mysql> select 2>3;
+-----+
| 2>3 |
+-----+
|   0   |
+-----+

# mysql> select 2>=3;
+------+
| 2>=3 |
+------+
|    0  |
+------+

# mysql> select 5 between 1 and 10;
+--------------------+
| 5 between 1 and 10 |
+--------------------+
|                  1 |
+--------------------+

# mysql> select 5 in (1,2,3,4,5);
+------------------+
| 5 in (1,2,3,4,5) |
+------------------+
|                1 |
+------------------+

# mysql> select 5 not in (1,2,3,4,5);
+----------------------+
| 5 not in (1,2,3,4,5) |
+----------------------+
|                    0 |
+----------------------+

# 
mysql> select null is NULL;
+--------------+
| null is NULL |
+--------------+
|            1 |
+--------------+
mysql> select ‘a‘ is NULL;
+-------------+
| ‘a‘ is NULL |
+-------------+
|           0 |
+-------------+

# mysql> select null IS NOT NULL;
+------------------+
| null IS NOT NULL |
+------------------+
|                0 |
+------------------+        

# mysql> select ‘a‘ IS NOT NULL;
+-----------------+
| ‘a‘ IS NOT NULL |
+-----------------+
|               1 |
+-----------------+

# mysql> select ‘12345‘ like ‘12%‘;
+--------------------+
| ‘12345‘ like ‘12%‘ |
+--------------------+
|                  1 |
+--------------------+

# mysql> select ‘12345‘ like ‘12_‘;
+--------------------+
| ‘12345‘ like ‘12_‘ |
+--------------------+
|                  0 |
+--------------------+

# mysql> select ‘beijing‘ REGEXP ‘jing‘;
+-------------------------+
| ‘beijing‘ REGEXP ‘jing‘ |
+-------------------------+
|                       1 |
+-------------------------+

# mysql> select ‘beijing‘ REGEXP ‘xi‘;
+-----------------------+
| ‘beijing‘ REGEXP ‘xi‘ |
+-----------------------+
|                     0 |
+-----------------------+

# mysql> select 2 and 0;
+---------+
| 2 and 0 |
+---------+
|       0 |
+---------+
   
# mysql> select 2 and 1;   
+---------+     
| 2 and 1 |      
+---------+      
|       1 |      
+---------+

# mysql> select 2 or 0;
+--------+
| 2 or 0 |
+--------+
|      1 |
+--------+

# mysql> select 2 or 1;
+--------+
| 2 or 1 |
+--------+
|      1 |
+--------+

# mysql> select 0 or 0;
+--------+
| 0 or 0 |
+--------+
|      0 |
+--------+

# mysql> select 1 || 0;
+--------+
| 1 || 0 |
+--------+
|      1 |
+--------+

# mysql> select not 1;
+-------+
| not 1 |
+-------+
|     0 |
+-------+

# mysql> select !0;
+----+
| !0 |
+----+
|  1 |
+----+

# mysql> select 1 xor 1;
+---------+
| 1 xor 1 |
+---------+
|       0 |
+---------+

# mysql> select 0 xor 0;
+---------+
| 0 xor 0 |
+---------+
|       0 |
+---------+

# mysql> select 1 xor 0;
+---------+
| 1 xor 0 |
+---------+
|       1 |
+---------+

# mysql> select null or 1;
+-----------+
| null or 1 |
+-----------+
|         1 |
+-----------+

# mysql> select 1 ^ 0;
+-------+
| 1 ^ 0 |
+-------+
|     1 |
+-------+

# 查询类型 cate_name 为 ‘超级本‘ 的商品名称 name 、价格 price ( where )
select name,price from goods where cate_name = "超级本";

# 显示商品的种类
# 1 分组的方式( group by ) 
select cate_name from goods group by cate_name;

# 2 去重的方法( distinct )
select distinct cate_name from goods;

# 求所有电脑产品的平均价格 avg ,并且保留两位小数( round )
select round(avg(price),2) from goods;

# 显示 每种类型 cate_name (由此可知需要分组)的 平均价格
select cate_name,avg(price) from goods group by cate_name;

#查询 每种类型 的商品中 最贵 max 、最便宜 min 、平均价 avg 、数量 count
select max(price),min(price),avg(price),count(*) from goods group by cate_name;

# 查询所有价格大于 平均价格 的商品，并且按 价格降序 排序 order desc
# 1 查询平局价格(avg_price)
select avg(price) as avg_price from goods;

# 2 使用子查询
select * from goods where price > (select avg(price) as avg_price from goods) order by price desc;

# 查询每种类型中最贵的电脑信息(难)
# 1 查找 每种类型 中 最贵的 max_price 价格
select cate_name,max(price) as max_price from goods group by cate_name;

# 2 关联查询 inner join 每种类型 中最贵的物品信息
select * from goods inner join(select cate_name,max(price) as max_price from goods group by cate_name) as max_price_goods
on goods.cate_name=max_price_goods.cate_name and goods.price=max_price_goods.max_price;

# 创建"商品分类"表
# 第一步    创建表 (商品种类表 goods_cates )
create table if not exists goods_cates(
id int unsigned primary key auto_increment,
name varchar(40) not null
);
# 第二步    同步 商品分类表 数据 将商品的所有 (种类信息) 写入到 (商品种类表) 中 按照 分组 的方式查询 goods 表中的所有 种类(cate_name)
select cate_name from goods group by cate_name;

# (注意) 把查询出来的 结果 写入 goods_cates 表里去 ( insert into ) 只插入name
insert into goods_cates(name) (select cate_name from goods group by cate_name);

# 第三部 同步 商品表 数据 通过 goods_cates 数据表来更新 goods 表
# 因为要通过 goods_cates表 更新 goods 表 所以要把两个表连接起来
select * from goods inner join goods_cates on goods.cate_name = goods_cates.name;

# 把 商品表 goods 中的 cate_name 全部替换成 商品分类表中的 商品id ( update ... set )
update (goods inner join goods_cates on goods.cate_name = goods_cates.name) set goods.cate_name = goods_cates.id;

# 第四部 修改表结构
# 查看表结构(注意 两个表中的 外键类型需要一致)
desc goods;

#修改表结构 alter table 字段名字不同 change,把 cate_name 改成 cate_id int unsigned not null
alter table goods change cate_name cate_id int unsigned not null;

# 创建 商品品牌表 goods_brands
# 第一步 创建 "商品品牌表" 表
# 第一种方式 先创建表
create table goods_brands (
id int unsigned primary key auto_increment,
name varchar(40) not null);
# 插入数据 brand_name(分组)
# 按照 分组 的方式查询 goods 表中的所有 种类(brand_name)
select brand_name from goods group by brand_name;

# (注意) 把查询出来的 结果 写入 goods_brands 表里去 ( insert into ) 只插入name
insert into goods_brands(name) (select brand_name from goods group by brand_name);

# 第二种方式 创建表的同时插入数据(了解,不建议使用)
create table goods_brands (
id int unsigned primary key auto_increment,
name varchar(40) not null) select brand_name as name from goods group by brand_name;
# 第二步 同步数据
# 通过goods_brands数据表来更新goods数据表 g.brand_name=b.id
update (goods inner join goods_brands on goods.brand_name = goods_brands.name) set goods.brand_name = goods_brands.id;

# 第三步 修改表结构
# 通过alter table语句修改表结构 brand_id int unsigned not null
alter table goods change brand_name brand_id int unsigned not null;

# 外键的使用(了解)
# 创建外键
# -- 向goods表里插入任意一条数据
insert into goods (name,cate_id,brand_id,price) values(‘老王牌拖拉机‘, 10, 10,‘6666‘);

# 约束 数据的插入 使用 外键 foreign key
alter table goods add foreign key (brand_id) references goods_brands(id);
alter table goods add foreign key (cate_id) references goods_cates(id);
alter table goods add foreign key(brand_id) references goods_brands(id);

# 失败原因 老王牌拖拉机 delete
delete from goods where name="老王牌拖拉机";
# 创建表的同时设置外键 (注意 goods_cates 和 goods_brands 两个表必须事先存在)
create table goods(
id int primary key auto_increment not null,
name varchar(40) default ‘‘,
price decimal(5,2),
cate_id int unsigned,
brand_id int unsigned,
is_show bit default 1,
is_saleoff bit default 0,
foreign key(cate_id) references goods_cates(id),
foreign key(brand_id) references goods_brands(id)
);

# 如何取消外键约束
#需要先获取外键约束名称,该名称系统会自动生成,可以通过查看表创建语来获取名称
show create table goods;

# 获取名称之后就可以根据名称来删除外键约束
alter table goods drop foreign key goods_ibfk_1;
alter table goods drop foreign key goods_ibfk_2;

# 总结:在实际开发中,很少会使用到外键约束,会极大的降低表更新的效率