MySQL数据库查询数据操作篇1到19篇

1.使用select从单个表中获取数据
mysql> use test_db;

mysql> create table fruits
    -> (
    -> f_id char(10)    not null,
    -> s_id int     not null,
    -> f_name   char(255)   not null,
    -> primary key(f_id)
    -> );
Query OK, 0 rows affected

2.插入如下数据，为select语句做铺垫
mysql> insert into fruits(f_id,s_id,f_name,f_price)
    -> values("a1",101,"apple",5.2),
    -> ("b1",102,"banana",6.2),
    -> ("c1",103,"caomei",7.2)
    -> ;
Query OK, 3 rows affected
Records: 3  Duplicates: 0  Warnings: 0

3.使用select语句查询指定字段f_id和f_name的数据
mysql> select f_id,f_name from fruits;
+------+--------+
| f_id | f_name |
+------+--------+
| a1   | apple  |
| b1   | banana |
| c1   | caomei |
+------+--------+
3 rows in set

4.从fruits表中查询所有字段的数据
mysql> select * from fruits;
+------+------+--------+---------+
| f_id | s_id | f_name | f_price |
+------+------+--------+---------+
| a1   |  101 | apple  | 5.2     |
| b1   |  102 | banana | 6.2     |
| c1   |  103 | caomei | 7.2     |
+------+------+--------+---------+
3 rows in set

5.用select语句指定所有字段。结果同select * from fruits;
mysql> select f_id,s_id,f_name,f_price from fruits;
+------+------+--------+---------+
| f_id | s_id | f_name | f_price |
+------+------+--------+---------+
| a1   |  101 | apple  | 5.2     |
| b1   |  102 | banana | 6.2     |
| c1   |  103 | caomei | 7.2     |
+------+------+--------+---------+
3 rows in set

6.查询单个字段
mysql> select f_name from fruits;
+--------+
| f_name |
+--------+
| apple  |
| banana |
| caomei |
+--------+
3 rows in set
7.查询多个字段
mysql> select f_name,f_price from fruits;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
| banana | 6.2     |
| caomei | 7.2     |
+--------+---------+
3 rows in set
8.查询指定记录
mysql> select f_name,f_price
    -> from fruits
    -> where f_price = 5.2
    -> ;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
+--------+---------+
1 row in set


mysql> select f_name,f_price
    -> from fruits
    -> where f_name = "apple"
    -> ;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
+--------+---------+
1 row in set


mysql> select f_name,f_price
    -> from fruits
    -> where f_price < 10
    -> ;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
| banana | 6.2     |
| caomei | 7.2     |
+--------+---------+
3 rows in set
9.带IN关键字查询
mysql> select s_id,f_name,f_price
    -> from fruits
    -> where s_id in (101,102)
    -> order by f_name
    -> ;
+------+--------+---------+
| s_id | f_name | f_price |
+------+--------+---------+
|  101 | apple  | 5.2     |
|  102 | banana | 6.2     |
+------+--------+---------+
2 rows in set


#在IN关键字前面加上NOT关键字，查询的结果与IN恰恰相反。
mysql> select s_id,f_name,f_price
    -> from fruits
    -> where s_id not in (101,102)
    -> order by f_name
    -> ;
+------+--------+---------+
| s_id | f_name | f_price |
+------+--------+---------+
|  103 | caomei | 7.2     |
+------+--------+---------+
1 row in set
10.带BETWEEN AND的范围查询
mysql> select f_name,f_price
    -> from fruits
    -> where f_price between 5.2 and 8.2
    -> ;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
| banana | 6.2     |
| caomei | 7.2     |
+--------+---------+
3 rows in set

11.带LIKE的字符匹配查询
(1)百分号通配符  '%' ,匹配任意长度的字符，甚至包括零字符
查询所有以'b'开头的水果：
mysql> select f_id,f_name
    -> from fruits
    -> where f_name like "b%"
    -> ;
+------+--------+
| f_id | f_name |
+------+--------+
| b1   | banana |
+------+--------+
1 row in set

查询以'b'开头，以'a'结尾的水果的名称：
mysql> select f_name
    -> from fruits
    -> where f_name like 'b%a'
    -> ;
+--------+
| f_name |
+--------+
| banana |
+--------+
1 row in set

（2）下划线通配符'_'，一次只能匹配任意一个字符。
查询以字母'e'结尾，且'e'前面只有4个字母的记录:
mysql> select f_name
    -> from fruits
    -> where f_name like 'b%a'
    -> ;
+--------+
| f_name |
+--------+
| banana |
+--------+
1 row in set

12.查询空值
查询customers表中的c_email为空的记录的c_id,c_name和c_email字段值：

mysql> select c_id,c_name,c_email from customers where c_email is null;
+-------+--------+---------+
| c_id  | c_name | c_email |
+-------+--------+---------+
| 10088 | oldboy | NULL    |
+-------+--------+---------+
1 row in set

查询customers表中的c_email不为空的记录的c_id,c_name和c_email字段值：

mysql> select c_id,c_name,c_email from customers where c_email is not null;
+-------+--------+-------------------+
| c_id  | c_name | c_email           |
+-------+--------+-------------------+
| 10086 | zgyd   | Liming@163.com    |
| 10087 | stars  | Jerry@hotmain.com |
+-------+--------+-------------------+
2 rows in set

13.带AND多条件查询
查询fruits表中查询s_id = 101且f_price大于等于5的水果价格和名称：
mysql> select f_id,f_price,f_name 
    -> from fruits
    -> where s_id = "101" and f_price >= 5
    -> ;
+------+---------+--------+
| f_id | f_price | f_name |
+------+---------+--------+
| a1   | 5.2     | apple  |
+------+---------+--------+
1 row in set


在fruits表中查询s_id = 101或102且f_price大于5且f_name = "apple"的水果价格和名称：
mysql> select f_id,f_price,f_name
    -> from fruits
    -> where s_id in("101","102") and f_price >= 5 and f_name = "apple"
    -> ;
+------+---------+--------+
| f_id | f_price | f_name |
+------+---------+--------+
| a1   | 5.2     | apple  |
+------+---------+--------+
1 row in set
14.带OR的多条件查询
查询s_id = 101或者s_id = 102的水果供应商的f_price和f_name:
mysql> select s_id,f_name,f_price from fruits where s_id = 101 or s_id = 102;
+------+--------+---------+
| s_id | f_name | f_price |
+------+--------+---------+
|  101 | apple  | 5.2     |
|  102 | banana | 6.2     |
+------+--------+---------+
2 rows in set

查询s_id = 101或者s_id = 102的水果供应商的f_price和f_name:
---》还可以：
mysql> select s_id,f_name,f_price
    -> from fruits
    -> where s_id in (101,102)
    -> ;
+------+--------+---------+
| s_id | f_name | f_price |
+------+--------+---------+
|  101 | apple  | 5.2     |
|  102 | banana | 6.2     |
+------+--------+---------+
2 rows in set

15.查询结果不重复
mysql> select distinct s_id from fruits;
+------+
| s_id |
+------+
|  101 |
|  102 |
|  103 |
+------+
3 rows in set

17.对查询结果排序

mysql> select f_name from fruits;
+--------+
| f_name |
+--------+
| apple  |
| banana |
| caomei |
+--------+
3 rows in set
单列排序：
mysql> select f_name from fruits order by f_name;
+--------+
| f_name |
+--------+
| apple  |
| banana |
| caomei |
+--------+
3 rows in set
多列排序：
mysql> select f_name,f_price from fruits order by f_name,f_price;
+--------+---------+
| f_name | f_price |
+--------+---------+
| apple  | 5.2     |
| banana | 6.2     |
| caomei | 7.2     |
+--------+---------+
3 rows in set

指定排序方向：
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：
mysql> select f_name,f_price from fruits order by f_price desc;
+--------+---------+
| f_name | f_price |
+--------+---------+
| caomei | 7.2     |
| banana | 6.2     |
| apple  | 5.2     |
+--------+---------+
3 rows in set

查询fruits表，先按f_price降序排序，再按f_name字段升序排序：
mysql> select f_price,f_name from fruits order by f_price desc,f_name;
+---------+--------+
| f_price | f_name |
+---------+--------+
| 7.2     | caomei |
| 6.2     | banana |
| 5.2     | apple  |
+---------+--------+
3 rows in set

18.分组查询
mysql> select s_id,count(*) as total from fruits group by s_id;
+------+-------+
| s_id | total |
+------+-------+
|  101 |     1 |
|  102 |     1 |
|  103 |     1 |
+------+-------+
3 rows in set

mysql> select s_id,group_concat(f_name) as name from fruits group by s_id;
+------+--------+
| s_id | name   |
+------+--------+
|  101 | apple  |
|  102 | banana |
|  103 | caomei |
+------+--------+
3 rows in set

mysql> select s_id,group_concat(f_name) as names
    -> from fruits
    -> group by s_id having count(f_name) > 1;
Empty set

mysql> select s_id,count(*) as total
    -> from fruits
    -> group by s_id with rollup
    -> ;
+------+-------+
| s_id | total |
+------+-------+
|  101 |     1 |
|  102 |     1 |
|  103 |     1 |
| NULL |     3 |
+------+-------+
4 rows in set
19.使用LIMIT限制查询结果的数量
显示fruits表查询结果的前4行：
mysql> select * from fruits limit 4;
+------+------+--------+---------+
| f_id | s_id | f_name | f_price |
+------+------+--------+---------+
| a1   |  101 | apple  | 5.2     |
| b1   |  102 | banana | 6.2     |
| c1   |  103 | caomei | 7.2     |
+------+------+--------+---------+
3 rows in set

这里的1是第二行，3总行数为3行。
mysql> select * from fruits limit 1,3;
+------+------+--------+---------+
| f_id | s_id | f_name | f_price |
+------+------+--------+---------+
| b1   |  102 | banana | 6.2     |
| c1   |  103 | caomei | 7.2     |
+------+------+--------+---------+
2 rows in set