怎么给MySQL增加Sequence管理功能

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-- Sequence 管理表
DROP TABLE IF EXISTS sequence;
CREATE TABLE sequence (
name VARCHAR(50) NOT NULL,
current_value INT NOT NULL,
increment INT NOT NULL DEFAULT 1,
PRIMARY KEY (name)
) ENGINE=InnoDB;

-- 取当前值的函数
DROP FUNCTION IF EXISTS currval;
DELIMITER $
CREATE FUNCTION currval (seq_name VARCHAR(50))
RETURNS INTEGER
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT ''
BEGIN
DECLARE value INTEGER;
SET value = 0;
SELECT current_value INTO value
FROM sequence
WHERE name = seq_name;
RETURN value;
END
$
DELIMITER ;

-- 取下一个值的函数
DROP FUNCTION IF EXISTS nextval;
DELIMITER $
CREATE FUNCTION nextval (seq_name VARCHAR(50))
RETURNS INTEGER
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT ''
BEGIN
UPDATE sequence
SET current_value = current_value + increment
WHERE name = seq_name;
RETURN currval(seq_name);
END
$
DELIMITER ;

-- 更新当前值的函数
DROP FUNCTION IF EXISTS setval;
DELIMITER $
CREATE FUNCTION setval (seq_name VARCHAR(50), value INTEGER)
RETURNS INTEGER
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT ''
BEGIN
UPDATE sequence
SET current_value = value
WHERE name = seq_name;
RETURN currval(seq_name);
END
$
DELIMITER ;

/*
-- 测试
INSERT INTO sequence VALUES ('TestSeq', 0, 1);
SELECT SETVAL('TestSeq', 10);
SELECT CURRVAL('TestSeq');
SELECT NEXTVAL('TestSeq');
*/

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