mysql 模拟一个自增序列

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mysql没有像oracle一样的sequence自增序列，需要我们自己维护一个。

CREATE TABLE sys_sequence (
  NAME varchar(50) NOT NULL,
  CURRENT_VALUE int(11) NOT NULL DEFAULT '',
  INCREMENT int(11) NOT NULL DEFAULT '',
  PRIMARY KEY (NAME)
);

INSERT INTO SYS_SEQUENCE(NAME,CURRENT_VALUE,INCREMENT) VALUES('diablo_seq', 1,1);

DROP FUNCTION IF EXISTS fun_currval;
DELIMITER $$
CREATE  FUNCTION fun_currval(seq_name VARCHAR(50)) RETURNS INT(11)
  BEGIN
    DECLARE VALUE INTEGER;
    SET VALUE=0;
    SELECT current_value INTO VALUE
    FROM sys_sequence
    WHERE NAME=seq_name;
    RETURN VALUE;
  END$$
DELIMITER ;

DROP FUNCTION IF EXISTS fun_nextval;
DELIMITER $$
CREATE  FUNCTION fun_nextval(seq_name varchar(50)) RETURNS int(11)
  BEGIN
    UPDATE sys_sequence
    SET CURRENT_VALUE = CURRENT_VALUE + INCREMENT
    where name=seq_name;
    return fun_currval(seq_name);
  END$$
DELIMITER ;