Question

我将列id定义为主键，但如何自动将其设置为大于最后一列？

Answer 1

您正在寻找AUTO_INCREMENT，您可以查看documentation here 您需要将id列设置为AUTO_INCREMENT

文档中的示例

CREATE TABLE animals (
     id MEDIUMINT NOT NULL AUTO_INCREMENT,
     name CHAR(30) NOT NULL,
     PRIMARY KEY (id)
) ENGINE=MyISAM;

Answer 2

你必须设置自动增量。

CREATE TABLE animals (
 id MEDIUMINT NOT NULL AUTO_INCREMENT,
 name CHAR(30) NOT NULL,
 PRIMARY KEY (id)
) ENGINE=MyISAM;

INSERT INTO animals (name) VALUES
('dog'),('cat'),('penguin'),
('lax'),('whale'),('ostrich');

SELECT * FROM animals;

 Which returns:

+----+---------+
| id | name    |
+----+---------+
|  1 | dog     |
|  2 | cat     |
|  3 | penguin |
|  4 | lax     |
|  5 | whale   |
|  6 | ostrich |
+----+---------+

http://dev.mysql.com/doc/refman/5.0/en/example-auto-increment.html mysql参考

Answer 3

"AUTO_INCREMENT" it ...

请参阅链接http://www.w3schools.com/sql/sql_autoincrement.asp

示例：以下SQL语句将“P_Id”列定义为“Persons”表中的自动增量主键字段：

CREATE TABLE Persons ( P_Id int NOT NULL AUTO_INCREMENT, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), PRIMARY KEY (P_Id) )

Answer 4

好的没注意到标签。

点击phpMyAdmin中的A_I复选框获取id列。

--- ---老

Oracle方式，触发序列：

CREATE sequence aic increment BY 1 start WITH 1;

CREATE TABLE blarg (
        id NUMBER(15,0) PRIMARY KEY,
        foobar VARCHAR2(255)
);

CREATE TRIGGER trigger ait BEFORE INSERT ON blarg
REFERENCING NEW AS NEW OLD AS OLD FOR EACH ROW
Begin
    SELECT aic.NEXTVAL INTO :NEW.id FROM DUAL;
End;

如何使我的sql主键自动计数？

4 个答案: