MySQL中怎么实现单表查询操作

发布时间：2022-02-13 14:09:58 所属栏目：编程来源：互联网

导读：这篇文章将为大家详细讲解有关MySQL中怎么实现单表查询操作，文章内容质量较高，因此小编分享给大家做个参考，希望大家阅读完这篇文章后对相关知识有一定的了解。创建fruits表： CREATE TABLE fruits ( f_id char(10) NOT NULL, s_id INT NOT NULL, f_name

这篇文章将为大家详细讲解有关MySQL中怎么实现单表查询操作，文章内容质量较高，因此小编分享给大家做个参考，希望大家阅读完这篇文章后对相关知识有一定的了解。

创建fruits表：

CREATE TABLE fruits
(
f_id char(10)   NOT NULL,
s_id INT NOT NULL,
f_name char(255)   NOT NULL,
f_price decimal(8,2) NOT NULL,
PRIMARY KEY(f_id)
) ;
INSERT INTO fruits (f_id, s_id, f_name, f_price)
VALUES('a1', 101,'apple',5.2),
('b1',101,'blackberry', 10.2),
('bs1',102,'orange', 11.2),
('bs2',105,'melon',8.2),
('t1',102,'banana', 10.3),
('t2',102,'grape', 5.3),
('o2',103,'coconut', 9.2),
('c0',101,'cherry', 3.2),
('a2',103, 'apricot',2.2),
('l2',104,'lemon', 6.4),
('b2',104,'berry', 7.6),
('m1',106,'mango', 15.6),
('m2',105,'xbabay', 2.6),
('t4',107,'xbababa', 3.6),
('m3',105,'xxtt', 11.6),
('b5',107,'xxxx', 3.6);
常用查询：

SELECT * FROM fruits;
select f_name,f_price from fruits;
select f_name,f_price from fruits where f_price=10.2;
select f_name,f_price from fruits where f_price<10;
select * from fruits where s_id in (101,102) order by f_name;
select * from fruits where s_id not in (101,102) order by f_name;
select f_name,f_price from fruits where f_price between 2.00 and 10.20;
select f_name,f_price from fruits where f_price not between 2.00 and 10.20;
select f_name,f_price from fruits where f_name like "b%";
select f_name,f_price from fruits where f_name like "%g%";
select f_name,f_price from fruits where f_name like "b%y";
select f_name,f_price from fruits where f_name like "____y";
创建customers表：

CREATE TABLE customers
(
c_id   int    NOT NULL AUTO_INCREMENT,
c_name char(50) NOT NULL,
c_address char(50) NULL,
c_city char(50) NULL,
c_zip   char(10) NULL,
c_contact char(50) NULL,
c_email char(255) NULL,
PRIMARY KEY (c_id)
);
INSERT INTO customers(c_id, c_name, c_address, c_city, c_zip, c_contact, c_email)
VALUES(10001, 'RedHook', '200 Street ', 'Tianjin', '300000', 'LiMing', 'LMing@163.com'),
(10002, 'Stars', '333 Fromage Lane', 'Dalian', '116000', 'Zhangbo','Jerry@hotmail.com'),
(10003, 'Netbhood', '1 Sunny Place', 'Qingdao', '266000', 'LuoCong', NULL),
(10004, 'JOTO', '829 Riverside Drive', 'Haikou', '570000', 'YangShan', 'sam@hotmail.com');
常用查询语句：

select c_id,c_name,c_email from customers where c_email is null;
select c_id,c_name,c_email from customers where c_email is not null;
select f_name,f_price from fruits where s_id=101 and f_price>=5;
select f_name,f_price from fruits where s_id in (101,102) and f_price >=5 and f_name="apple";
select f_name,f_price from fruits where s_id=101 or s_id=102;
使用in操作更加简洁明了

select f_name,f_price
from fruits
where s_id in (101 ,102);
字段不重复

SELECT DISTINCT s_id FROM fruits;
select f_name from fruits ORDER BY f_name;
如果第一列数据中没有相同值，将不再对第二列进行排序。

SELECT f_name, f_price
FROM fruits
ORDER BY f_name, f_price;
按价格降序排列,desc为降序，默认为升序。

SELECT f_name, f_price FROM fruits ORDER BY f_price desc;
SELECT f_name, f_price FROM fruits ORDER BY f_price desc,f_name;
SELECT s_id, COUNT(*) AS Total FROM fruits GROUP BY s_id;
SELECT s_id, GROUP_CONCAT(f_name) AS Names FROM fruits GROUP BY s_id;
使用having过滤分组

SELECT s_id, GROUP_CONCAT(f_name) AS Names
FROM fruits
GROUP BY s_id having count(f_name)>1;
在group by 子句中使用with rollup

SELECT s_id, COUNT(*) AS Total FROM fruits GROUP BY s_id WITH ROLLUP;
SELECT * from fruits group by s_id,f_name;
创建orderitems表：

CREATE TABLE orderitems
(
o_num   int     NOT NULL,
o_item   int     NOT NULL,
f_id    char(10)   NOT NULL,
quantity int     NOT NULL,
item_price decimal(8,2) NOT NULL,
PRIMARY KEY (o_num,o_item)
) ;
INSERT INTO orderitems(o_num, o_item, f_id, quantity, item_price)
VALUES(30001, 1, 'a1', 10, 5.2),
(30001, 2, 'b2', 3, 7.6),
(30001, 3, 'bs1', 5, 11.2),
(30001, 4, 'bs2', 15, 9.2),
(30002, 1, 'b3', 2, 20.0),
(30003, 1, 'c0', 100, 10),
(30004, 1, 'o2', 50, 2.50),
(30005, 1, 'c0', 5, 10),
(30005, 2, 'b1', 10, 8.99),
(30005, 3, 'a2', 10, 2.2),
(30005, 4, 'm1', 5, 14.99);
常用查询语句：

SELECT o_num, SUM(quantity * item_price) AS orderTotal
FROM orderitems
GROUP BY o_num
HAVING SUM(quantity*item_price) >= 100;
SELECT o_num, SUM(quantity * item_price) AS orderTotal
FROM orderitems
GROUP BY o_num
HAVING SUM(quantity*item_price) >= 100
order by ordertotal;
SELECT * From fruits LIMIT 8;
从第五行开始，读取3行

SELECT * From fruits LIMIT 4,3;
【例.1】从fruits表中检索所有字段的数据

SELECT * FROM fruits;
SELECT f_id, s_id ,f_name, f_price FROM fruits;
【例.2】查询当前表中f_name列所有水果名称，输入如下语句：

SELECT f_name FROM fruits;
【例.3】例如，从fruits表中获取f_name和f_price两列，输入如下语句：

SELECT f_name, f_price FROM fruits;
【例.4】查询价格为10.2元的水果的名称，输入如下语句：

SELECT f_name, f_price
FROM fruits
WHERE f_price = 10.2;
【例.5】查找名称为“apple”的水果的价格,输入如下语句：

SELECT f_name, f_price
FROM fruits
WHERE f_name = 'apple';
【例.6】查询价格小于10的水果的名称，输入如下语句：

SELECT f_name, f_price
FROM fruits
WHERE f_price < 10;
【例.7】s_id为101和102的记录，输入如下语句：

SELECT s_id,f_name, f_price
FROM fruits
WHERE s_id IN (101,102)
ORDER BY f_name;
【例.8】查询所有s_id不等于101也不等于102的记录，输入如下语句：

SELECT s_id,f_name, f_price
FROM fruits
WHERE s_id NOT IN (101,102)
ORDER BY f_name;
【例.9】查询价格在2.00元到10.5元之间水果名称和价格

SELECT f_name, f_price
FROM fruits
WHERE f_price BETWEEN 2.00 AND 10.20;
【例.10】查询价格在2.00元到10.5元之外的水果名称和价格

SELECT f_name, f_price
FROM fruits
WHERE f_price NOT BETWEEN 2.00 AND 10.20;
【例.11】查找所有以‘b'字母开头的水果，输入如下语句：

SELECT f_id, f_name
FROM fruits
WHERE f_name LIKE 'b%';
【例.12】在fruits表中，查询f_name中包含字母‘g'的记录

SELECT f_id, f_name
FROM fruits
WHERE f_name LIKE '%g%';
【例.13】查询以‘b'开头，并以‘y'结尾的水果的名称

SELECT f_name
FROM fruits
WHERE f_name LIKE 'b%y';
【例7.14】在fruits表中，查询以字母‘y'结尾，且‘y'前面只有4个字母的记录

SELECT f_id, f_name
FROM fruits
WHERE f_name LIKE '____y';
【例.15】查询customers表中c_email为空的记录的c_id、c_name和c_email字段值：

SELECT c_id, c_name,c_email
FROM customers
WHERE c_email IS NULL;
【例.16】查询customers表中c_email不为空的记录的c_id、c_name和c_email字段值

SELECT c_id, c_name,c_email
FROM customers
WHERE c_email IS NOT NULL;
【例.17】在fruits表中查询s_id = ‘101'，并且f_price大于5的记录价格和名称

SELECT f_id, f_price, f_name
FROM fruits
WHERE s_id = '101' AND f_price >=5;
【例.18】在fruits表中查询s_id = ‘101'或者'102'，并且f_price大于5，并且f_name='apple'的记录价格和名称

SELECT f_id, f_price, f_name
FROM fruits
WHERE s_id IN('101', '102') AND f_price >= 5 AND f_name = 'apple';
【例.19】查询s_id=101或者s_id=102的水果供应商的f_price和f_name，SQL语句如下：

SELECT s_id,f_name, f_price
FROM fruits
WHERE s_id = 101 OR s_id = 102;
【例.20】查询s_id=101或者s_id=102的水果供应商的f_price和f_name

SELECT s_id,f_name, f_price
FROM fruits
WHERE s_id IN(101,102);
【例.21】查询fruits表中s_id字段的值，并返回s_id字段值不得重复

SELECT DISTINCT s_id FROM fruits;
【例.22】查询fruits表的f_name字段值，并对其进行排序

select f_name from fruits ORDER BY f_name;
【例.23】查询fruits表中的f_name和f_price字段，先按f_name排序，再按f_price排序

SELECT f_name, f_price
FROM fruits
ORDER BY f_name, f_price;
【例.24】查询fruits表中的f_name和f_price字段，对结果按f_price降序方式排序

SELECT f_name, f_price
FROM fruits
ORDER BY f_price DESC;
【例.25】查询fruits表，先按f_price降序排序，再按f_name字段升序排序，SQL语句如下：

SELECT f_price, f_name
FROM fruits
ORDER BY f_price DESC, f_name;
【例.26】根据s_id对fruits表中的数据进行分组

SELECT s_id, COUNT(*) AS Total
FROM fruits
GROUP BY s_id;
【例.27】根据s_id对fruits表中的数据进行分组，将每个供应商的水果名称显示出来

SELECT s_id, GROUP_CONCAT(f_name) AS Names
FROM fruits
GROUP BY s_id;
【例.28】根据s_id对fruits表中的数据进行分组，并显示水果种类大于1的分组信息

SELECT s_id, GROUP_CONCAT(f_name) AS Names
FROM fruits
GROUP BY s_id HAVING COUNT(f_name) > 1;
【例.29】根据s_id对fruits表中的数据进行分组，并显示记录数量

SELECT s_id, COUNT(*) AS Total
FROM fruits
GROUP BY s_id WITH ROLLUP;
【例.30】根据s_id和f_name字段对fruits表中的数据进行分组， SQL语句如下，

SELECT * from fruits group by s_id,f_name;
【例.31】查询订单价格大于100的订单号和总订单价格

SELECT o_num, SUM(quantity * item_price) AS orderTotal
FROM orderitems
GROUP BY o_num
HAVING SUM(quantity*item_price) >= 100;
【例.32】显示fruits表查询结果的前4行，输入如下语句：

SELECT * From fruits LIMIT 4;
【例.33】在fruits 表中，使用LIMIT子句，返回从第5个记录开始的，行数长度为3的记录

SELECT * From fruits LIMIT 4, 3;
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