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  • mysql 函数模拟序列

    mysql本身不提供序列机制,但是可以通过函数来模拟实现序列

    CREATE TABLE IF NOT EXISTS `sequence`  (
      `id` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
      `current_value` int(11) NULL DEFAULT NULL,
      `increment` int(11) NOT NULL DEFAULT '1',
      PRIMARY KEY (`id`) USING BTREE
    ) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci;
    
    INSERT INTO `sequence` (`id`, `current_value`, `increment`) VALUES ('demo', 0, 1);
    
    DROP FUNCTION IF EXISTS `current_sequence`;  
    DELIMITER //  
    CREATE  FUNCTION `current_sequence`(seq_id VARCHAR(255)) RETURNS int(11)  
        READS SQL DATA  
        DETERMINISTIC  
    BEGIN  
        DECLARE VALUE INTEGER;  
        SET VALUE = 0;  
        SELECT current_value INTO VALUE FROM sequence WHERE id = seq_id;  
        RETURN VALUE;  
    END//  
    DELIMITER ;
    
    
    DROP FUNCTION IF EXISTS `next_sequence`;  
    DELIMITER //  
    CREATE  FUNCTION `next_sequence`(seq_id VARCHAR(255)) RETURNS int(11)  
        DETERMINISTIC  
    BEGIN  
    UPDATE sequence SET current_value = current_value + increment WHERE id = seq_id;  
    RETURN current_sequence(seq_id);  
    END//  
    DELIMITER ;
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  • 原文地址:https://www.cnblogs.com/relucent/p/10215729.html
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