Mysql中的序列主要用於主鍵,主鍵是遞增的字段,不可重複。
Mysql與Oracle不同的是,它不支持原生態的sequence,需要用表和函數的組合來實現類似序列的功能。
1.首先創建序列的主表
/*
Navicat Premium Data Transfer
Source Server : MySql_192.168.10.7
Source Server Type : MySQL
Source Server Version : 100113
Source Host : 192.168.10.7:3306
Source Schema : config_fao_atp
Target Server Type : MySQL
Target Server Version : 100113
File Encoding : 65001
Date: 17/04/2020 17:38:44
*/
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for sequence
-- ----------------------------
DROP TABLE IF EXISTS `sequence`;
CREATE TABLE `sequence` (
`name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`current_value` int(11) NOT NULL,
`increment` int(11) NOT NULL DEFAULT 1,
PRIMARY KEY (`name`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;
-- ----------------------------
-- Records of sequence
-- ----------------------------
INSERT INTO `sequence` VALUES ('artableSeq', 10021776, 1);
SET FOREIGN_KEY_CHECKS = 1;
其次創建如下三個函數,它們的功能分別是:查詢當前序列值、查詢下一個序列值、設置序列的起始值。
/*
Navicat Premium Data Transfer
Source Server : MySql_192.168.10.7
Source Server Type : MySQL
Source Server Version : 100113
Source Host : 192.168.10.7:3306
Source Schema : config_fao_atp
Target Server Type : MySQL
Target Server Version : 100113
File Encoding : 65001
Date: 17/04/2020 17:38:44
*/
-- ----------------------------
-- Function structure for currval
-- ----------------------------
DROP FUNCTION IF EXISTS `currval`;
DELIMITER ;;
CREATE DEFINER=`root`@`%` FUNCTION `currval`(seq_name VARCHAR(50)) RETURNS int(11)
DETERMINISTIC
BEGIN
DECLARE value INTEGER;
SET value = 0;
SELECT current_value INTO value
FROM sequence
WHERE name = seq_name;
RETURN value;
END
;;
DELIMITER ;
-- ----------------------------
-- Function structure for nextval
-- ----------------------------
DROP FUNCTION IF EXISTS `nextval`;
DELIMITER ;;
CREATE DEFINER=`root`@`%` FUNCTION `nextval`(seq_name VARCHAR(50)) RETURNS int(11)
DETERMINISTIC
BEGIN
UPDATE sequence
SET current_value = current_value + increment
WHERE name = seq_name;
RETURN currval(seq_name);
END
;;
DELIMITER ;
-- ----------------------------
-- Function structure for setval
-- ----------------------------
DROP FUNCTION IF EXISTS `setval`;
DELIMITER ;;
CREATE DEFINER=`root`@`%` FUNCTION `setval`(seq_name VARCHAR(50), value INTEGER) RETURNS int(11)
DETERMINISTIC
BEGIN
UPDATE sequence
SET current_value = value
WHERE name = seq_name;
RETURN currval(seq_name);
END
;;
DELIMITER ;
3.最後初始化序列數據,測試序列功能。
----添加一個sequence名稱和初始值,以及自增幅度 添加一個名爲filegenSeq 的自增序列
INSERT INTO sequence VALUES ('filegenSeq', 10000000, 1);
---設置指定sequence的初始值 這裏設置filegenSeq 的初始值爲10
SELECT SETVAL('filegenSeq', 10000000);
--查詢指定sequence的當前值 這裏是獲取filegenSeq當前值
SELECT CURRVAL('filegenSeq');
--查詢指定sequence的下一個值 這裏是獲取filegenSeq下一個值
SELECT NEXTVAL('filegenSeq');