如何创建由年份和数字组成的自动增量 ID 号,例如:“2012-0001”如果我输入其他数据,它将自动增量为“2012-0002”。
谢谢你!
使用 MyISAM,您可以做到这一点...
CREATE TABLE myisam_example(year INT NOT NULL,id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(year,id)) ENGINE=MyISAM;
INSERT INTO myisam_example VALUES (2012,NULL);
INSERT INTO myisam_example VALUES (2012,NULL);
INSERT INTO myisam_example VALUES (2012,NULL);
INSERT INTO myisam_example VALUES (2012,NULL);
INSERT INTO myisam_example VALUES (2012,NULL);
INSERT INTO myisam_example VALUES (2013,NULL);
INSERT INTO myisam_example VALUES (2013,NULL);
INSERT INTO myisam_example VALUES (2013,NULL);
INSERT INTO myisam_example VALUES (2013,NULL);
INSERT INTO myisam_example VALUES (2013,NULL);
SELECT * FROM myisam_example;
+------+----+
| year | id |
+------+----+
| 2012 | 1 |
| 2012 | 2 |
| 2012 | 3 |
| 2012 | 4 |
| 2012 | 5 |
| 2013 | 1 |
| 2013 | 2 |
| 2013 | 3 |
| 2013 | 4 |
| 2013 | 5 |
+------+----+
SELECT *
FROM myisam_example
WHERE CONCAT(year,'-',LPAD(id,5,0)) = '2012-00004';
+------+----+
| year | id |
+------+----+
| 2012 | 4 |
+------+----+
——对可怜的指数进行片刻的沉思
SET @sql = CONCAT('SELECT * FROM myisam_example WHERE CONCAT(year,\'-\',LPAD(id,5,0)) = ?');
PREPARE stmnt1 FROM @sql;
SET @a = '2012-00004';
EXECUTE stmnt1 USING @a;
+------+----+
| year | id |
+------+----+
| 2012 | 4 |
+------+----+
DEALLOCATE PREPARE stmnt1;
...并更进一步(因为我认为是时候知道如何在存储过程中使用准备好的语句了)...
DROP PROCEDURE fetchid;
DELIMITER $$
CREATE PROCEDURE fetchid(IN a VARCHAR(10))
BEGIN
SET @sql = CONCAT('SELECT * FROM myisam_example WHERE CONCAT(year,\'-\',LPAD(id,5,0)) = ?');
PREPARE stmnt1 FROM @sql;
SET @a = a;
EXECUTE stmnt1 USING @a;
DEALLOCATE PREPARE stmnt1;
END $$
DELIMITER ;
CALL fetchid('2012-00004');
+------+----+
| year | id |
+------+----+
| 2012 | 4 |
+------+----+
你将不得不编写一个程序来做到这一点。Strawberry 的解决方案向您展示了在 SQL 端需要做什么,但是您必须编写接口(非 sql)来拆分输入,这样当用户输入 2012-0001 时,查询字符串会显示类似“WHERE年 = 2012 并且 ID = 0001"
如果您要问是否可以在表格中有一个可以包含连字符但自动递增的列,答案是否定的。