我以为我正在目睹一些奇怪的行为。插入记录后，LAST_INSERT_ID()给我的结果不正确。
然后我读了http://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_last-insert-id
对于存储的更改值的函数和触发器，值为 当函数或触发器结束时恢复，因此遵循以下语句 不会看到更改的值。
是否有其他方法可以在触发器之外获取自动增量ID？
-- MySQL Script generated by MySQL Workbench
-- 07/08/16 05:58:42
-- Model: New Model Version: 1.0
SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES';
-- -----------------------------------------------------
-- Schema mydb
-- -----------------------------------------------------
CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ;
USE `mydb` ;
-- -----------------------------------------------------
-- Table `mydb`.`a`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`a` (
`id` INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`))
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`t`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`t` (
`a_id` INT NOT NULL,
`id` INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`, `a_id`),
CONSTRAINT `fk_t1_a1`
FOREIGN KEY (`a_id`)
REFERENCES `mydb`.`a` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`inc`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`inc` (
`a_id` INT NOT NULL,
`id` INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`a_id`, `id`))
ENGINE = MyISAM;
SET SQL_MODE=@OLD_SQL_MODE;
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
USE `mydb`;
DELIMITER $$
USE `mydb`$$
CREATE TRIGGER `t_BINS` BEFORE INSERT ON `t` FOR EACH ROW
BEGIN
INSERT INTO inc(a_id) VALUES(NEW.a_id);
SET NEW.id=LAST_INSERT_ID();
END$$
DELIMITER ;
测试
mysql> INSERT INTO a(id) VALUES(1),(2),(3);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> INSERT INTO t(a_id)VALUES(1);
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO t(a_id)VALUES(1);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO t(a_id)VALUES(1);
Query OK, 1 row affected (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 5 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM inc;
+------+----+
| a_id | id |
+------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
+------+----+
3 rows in set (0.00 sec)
mysql> SELECT * FROM t;
+------+----+
| a_id | id |
+------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
+------+----+
3 rows in set (0.00 sec)
mysql> INSERT INTO t(a_id)VALUES(1);
Query OK, 1 row affected (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 5 |
+------------------+
1 row in set (0.00 sec)
mysql> INSERT INTO t(a_id)VALUES(2);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO t(a_id)VALUES(2);
Query OK, 1 row affected (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 5 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM t;
+------+----+
| a_id | id |
+------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 2 | 1 |
| 2 | 2 |
+------+----+
6 rows in set (0.00 sec)
mysql> SELECT * FROM inc;
+------+----+
| a_id | id |
+------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 2 | 1 |
| 2 | 2 |
+------+----+
6 rows in set (0.00 sec)
mysql> INSERT INTO inc(a_id)VALUES(2);
Query OK, 1 row affected (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 3 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM inc;
+------+----+
| a_id | id |
+------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
+------+----+
7 rows in set (0.00 sec)
mysql>