如何在MySQL中创建具有自引用字段的表？

在GTFS中,字段parent_station来自stop_id(自引用)或NULL.例如(请注意,parent_station可能为NULL),

SELECT stop_id, stop_name, parent_station FROM stops where stop_id='1970324837184617' OR parent_station='1970324837184617';

+------------------+----------------------+------------------+
| stop_id          | stop_name            | parent_station   |
+------------------+----------------------+------------------+
| 1970324837184617 | Saint Agne-SNCF      |                  |
| 3377699720880648 | Saint Agne-SNCF      | 1970324837184617 |
| 3377699720880649 | Saint Agne-SNCF      | 1970324837184617 |
| 3377699722011100 | Saint Agne-SNCF      | 1970324837184617 |
| 3377699722011101 | Saint Agne-SNCF      | 1970324837184617 |
| 3377699722914835 | Saint Agne Gare SNCF | 1970324837184617 |
+------------------+----------------------+------------------+
6 rows in set (0,01 sec)

我创建了一个自引用表：

CREATE TABLE `stops` (
    stop_id VARCHAR(255) NOT NULL PRIMARY KEY,
    stop_code VARCHAR(255),
    stop_name VARCHAR(255),
    stop_desc VARCHAR(255),
    stop_lat DECIMAL(8,6),
    stop_lon DECIMAL(8,6),
    location_type INT(2),
    parent_station VARCHAR(255),
    -- the field `parent_station` might be blank (NULL)
    FOREIGN KEY parent_station REFERENCES stops(stop_id)  -- self-referential table fields
);

但遇到这个问题,

ERROR 1064 (42000) at line 99: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘FOREIGN KEY parent_station REFERENCES stops(stop_id)
)’ at line 11

在@Awita的帮助下,我更正了语法并成功创建了表.

FOREIGN KEY (parent_station) REFERENCES stops(stop_id) 

但是在加载本地数据时会出现一个新问题.

LOAD DATA LOCAL INFILE 'stops.txt' INTO TABLE stops FIELDS TERMINATED BY ',' IGNORE 1 LINES;

错误：

ERROR 1452 (23000) at line 140: Cannot add or update a child row: a foreign key constraint fails (`paris_gtfs`.`stops`, CONSTRAINT `stops_ibfk_1` FOREIGN KEY (`parent_station`) REFERENCES `stops` (`stop_id`))

此问题是由NULL parent_station引起的？

解决方法:

这是一个简单的语法错误.试试这个：

FOREIGN KEY (parent_station) REFERENCES stops(stop_id) 

标签：mysql,foreign-keys,create-table,self-reference,gtfs
来源： https://codeday.me/bug/20190528/1167579.html