Question

我有一个MySql函数，它接受3个参数。最后一个参数是一个查询本身，我可以使用PREPARE（？）执行，至少如果它没有多个结果。我想循环遍历从PREPARED语句返回的所有结果。

我该怎么做？我在考虑使用CURSOR，但我能找到的是，在PREPARED变量语句中使用CURSOR是不可能的。

我想要实现的目标如下：我在申请中看到了结果。结果被分页。 2.我想搜索特定的行，找到它所属的页面，并将其放入视图中。 3.结果视图可以通过多种方式进行过滤和排序，因此MySql函数的第三个参数是查询结果视图。

希望我说清楚，否则请告诉我。

到目前为止，我有以下内容： DELIMITER $$＃否则你不能用分号来结束一行

/*
The bar graph (clsBarGraph) shows cows in pages.
If you wish to search for a page with a certain Cow ID you need to do alot of things.
Therefore this function is created, to do the heavy lifting all in the database engine.accessible
@param LongCowID The long cow ID of the cow you wish to get the page for
@param ItemsPerPage To determine on what page a cow comes, it is necessary to known how many cows will fit into a page
@param SelectQuery The query that was used to view the data in the BarGraph. This determines ordering, which cows to have in the resultset to limit on, etc.
        This should be without the limit
@return The page number to set the view to, or -1 if the cow does not exist.
*/
CREATE FUNCTION `GetPageForCowID`(LongCowID INT, ItemsPerPage INT, SelectQuery VARCHAR(255))
RETURNS INT
BEGIN
DECLARE `page` INT;

/* Prepares queries to execute */
PREPARE stmt_CheckIfCowExists FROM 'SELECT COUNT(`Long_Cow_ID`) as `rows` FROM `cow_data` INTO @NumberOfRows';
EXECUTE stmt_CheckIfCowExists;
IF @NumberOfRows = 1 THEN 
    /* The cow does nto exist */
    SET `page` = -1;
ELSE
    /* The cow does exist */
    /* Get all the cows used in the view of the data, without a limit and put it into a variable */
    SET @SelectQuery = CONCAT(@SelectQuery, ' INTO @CowsForDataView');
    PREPARE stmt_SelectDataForView FROM @SelectQuery;
    EXECUTE stmt_SelectDataForView;
    SELECT COUNT(*) FROM stmt_SelectDataForView;

    DEALLOCATE PREPARE stmt_SelectDataForView;
END if;

/* Clean Up */
deallocate PREPARE stmt_CheckIfCowExists;
return `page`;
END

提前感谢。

Answer 1

将结果放入临时表：

SET @sql := CONCAT('CREATE TEMPORARY TABLE tmp_GetPageForCowID ', SelectQuery);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

然后可以将光标迭代到临时表的内容上。

MySql PREPARE stmt FROM [function argument]和CURSORs

1 个答案: