MySQL中怎么实现单表查询操作

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_pricefrom fruitswhere 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_priceFROM fruitsORDER 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 NamesFROM fruitsGROUP 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 orderTotalFROM orderitemsGROUP BY o_numHAVING SUM(quantity*item_price) >= 100;SELECT o_num, SUM(quantity * item_price) AS orderTotalFROM orderitemsGROUP BY o_numHAVING SUM(quantity*item_price) >= 100order 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_nameFROM fruitsWHERE 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_nameFROM fruitsWHERE 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_nameFROM fruitsWHERE 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_nameFROM fruitsWHERE 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_emailFROM customersWHERE 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_emailFROM customersWHERE 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_nameFROM fruitsWHERE 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_nameFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsWHERE 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_priceFROM fruitsORDER 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_priceFROM fruitsORDER 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_nameFROM fruitsORDER 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 TotalFROM fruitsGROUP 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 NamesFROM fruitsGROUP 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 NamesFROM fruitsGROUP 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 TotalFROM fruitsGROUP 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 orderTotalFROM orderitemsGROUP BY o_numHAVING 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;

关于MySQL中怎么实现单表查询操作就分享到这里了，希望以上内容可以对大家有一定的帮助，可以学到更多知识。如果觉得文章不错，可以把它分享出去让更多的人看到。