Question

对于模糊的标题抱歉，这是我的问题。我有DB2的存储过程，我试图转换为MySQL。我想知道我是否可以将游标声明中的SELECT语句写为字符串变量。例如，对于DB2，我有这个：

(...)
-- Declare cursors
DECLARE c_very_init CURSOR WITH RETURN FOR s_very_init;
DECLARE c_date      CURSOR WITH RETURN FOR s_date;

DECLARE CONTINUE HANDLER FOR not_found
    SET at_end = 1;

-- In case the_date is 0, retrieve the first date
IF the_date = 0 THEN
    SET sql_end_date = '
        SELECT DATE 
            FROM ACCOUNTS 
        WHERE REF = ''' || the_ref || ''' 
            ORDER BY ID ASC FETCH FIRST 1 ROWS ONLY';
    PREPARE s_date FROM sql_end_date;
    OPEN c_date;
    FETCH FROM c_date INTO data_ins;
    SET the_last_date = data_ins;
    CLOSE c_date;
ELSE
    SET the_last_date = the_date;
END IF;

-- Get the 'very' initial value
SET sql_very_init = '
        SELECT in, out 
            FROM MOVEMENTS 
        WHERE REF = ''' || the_ref || ''' 
            AND DATE < ' || the_last_date;
PREPARE s_very_init FROM sql_very_init;
OPEN c_very_init;
FETCH FROM c_very_init INTO dare, avere;

-- Loop through the results
(...)

我声明了一个c_very_init游标，但是在SP中的游标声明时，我仍然不知道完整的select语句，因为我需要获取（如果需要）the_last_date值。我似乎不能这样做：

DECLARE c_very_init CURSOR WITH RETURN FOR s_very_init;

使用MySQL，语法直接在声明中使用语句：

DECLARE c_very_init CURSOR FOR SELECT blaablaa...;

我错了吗？

谢谢。法比安

Answer 1

不，你不能用这种方式声明游标。但如果'the_ref'是一个变量，你就可以这样做 -

...
DECLARE the_ref INT DEFAULT 10;
DECLARE cur1 CURSOR FOR SELECT column1 FROM table1 WHERE column1 = the_ref;
...

MySQL存储过程：游标声明

1 个答案: