Frases comuns do MySql

1. Defina o ID da chave primária para incrementar AUTO_INCREMENT ou IDENTITY

uma:

创建默认以1开头的自增长字段
 ALTER TABLE  company_home CHANGE id id INT AUTO_INCREMENT;

以X开头：
 ALTER TABLE  company_home CHANGE id id INT AUTO_INCREMENT=X;

以X开头 以3增长：
 ALTER TABLE  company_home CHANGE id id INT  AUTO_INCREMENT(X,3)/IDENTITY(X,3);

---

b:

CREATE TABLE stu(
sid INT PRIMARY KEY AUTO_INCREMENT,
sname VARCHAR(20),
age INT,
gender VARCHAR(10)
);

3. Notas da instrução SQL: -

-- ALTER TABLE  company_home CHANGE id id INT AUTO_INCREMENT;

4. Modifique os dados:

UPDATE company_home
 SET busyabout='7',introduce='9',enviroment='10'
WHERE id=2;

5. O que é consultado é o número de linhas em cada tabela

select COUNT(id) FROM Company_Home ORDER BY id DESC;

6. Consulta em ordem decrescente

 SELECT  id FROM Company_Home ORDER BY id DESC;

7. Consulte as primeiras linhas de dados

1、SELECT   *   FROM   Company_Home LIMIT   5; 
2、 select top 5 * from table where id not in (select top 10 id from table) //查出前5条数据 并且这5条数据不属于前10条数据内 也就是11-15
select top 5 * from table where id not in (select top 5 id from table ORDER BY ID DESC) ORDER BY ID DESC//查出后5条数据 并且不在后5条数据内 20条数据 查出来的也是11-152个TOP的数字动态变更就是一个翻页效果使用的SQL了

3、select * from 表名 where id between 10 and 15 order by id desc 
4、SELECT  * FROM Company_Home WHERE 1=1 
AND id NOT IN(SELECT id FROM Company_Home WHERE id between 5 and 10 ORDER BY id DESC)
AND Introduce LIKE '%2%'

8 、 onde 1 = 1

这个，只是为后面有可能有不确定的条件而加的;比如有其他条件就可以 and ...了
不用判断原来是不是有过条件，只要是and连接sql语句就可以了

 

9. Uso de AS

A：代替字段
 SELECT SUM(number) as number 
 FROM firecontrol GROUP BY type

B:对于查询的集合 视作新表：
select * from (select * from [Table] where xxx) as newTable --此时就可以用as，而且可以省略