Question

我有两个表，A和B.当在表B中插入新行时，如何插入FK作为表A中记录的引用？

我有两张下表：

--
-- Table structure for table `sector`
--

CREATE TABLE IF NOT EXISTS `sector` (
  `sector_id` int(11) NOT NULL AUTO_INCREMENT,
  `sector_name` varchar(100) NOT NULL,
  `sector_url` varchar(500) NOT NULL,
  PRIMARY KEY (`sector_id`),
  UNIQUE KEY `sector_id` (`sector_id`,`sector_name`,`sector_url`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;


CREATE TABLE IF NOT EXISTS `constituent` (
  `constituent_id` int(11) NOT NULL AUTO_INCREMENT,
  `constituent_name` varchar(100) DEFAULT '',
  `constituent_ticker` varchar(10) NOT NULL,
  `constituent_isin_number` varchar(50) DEFAULT '',
  `constituent_currency` varchar(10) DEFAULT '',
  `sector_id` int(11) NOT NULL,
  PRIMARY KEY (`constituent_id`),
  KEY `sector_id` (`sector_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;


--
-- Constraints for table `constituent`
--
ALTER TABLE `constituent`
  ADD CONSTRAINT `constituent_ibfk_1` FOREIGN KEY (`sector_id`) REFERENCES `sector` (`sector_id`);

当我执行插入操作时，如何构造查询，以便在插入表'component'时，我使用'sector'的主键？

INSERT into constituent (constituent_name, constituent_ticker, constituent_isin_number, constituent_currency, sectorFK) 
values ("the name", "the ticker", "the number", "the currency", "the foreign key???")

Answer 1

为了能够在插入表B后获取主键值，为了将其插入到表A中，您可以使用last_insert_id()函数，参数返回为AUTO_INCREMENT列设置的上次自动生成的值：

例如：

insert into B(col)
  values(1);

insert into A(t1_id, col)
  values(last_insert_id(), 2);

insert into A(t1_id, col)
  values(last_insert_id(), 3);

SQLFIddle Demo

Answer 2

假设有一个扇区有扇区'扇区1'，你可以这样做。

INSERT into constituent (constituent_name, constituent_ticker, constituent_isin_number, constituent_currency, sector_id) (select 'the name', 'the ticker', 'the number', 'the currency', sector_id from sector where sector_name = "sector 1");

如何在一行中插入外键？

2 个答案: