SQL：不允许从函数返回结果集

Question

我有一个名为compare_two_regions的SQL函数，它返回数据类型BIT，我想在名为compare_two_series的函数上调用此函数。 我简化了这个函数，我只想从compare_two_regions函数返回值。我仍然希望在循环中调用compare_two_regions函数，但即使在这个简化的情况下：

DELIMITER $$

create function compare_two_series( serieA varchar(255), serieB varchar(255)) 
returns BIT 
begin
declare result BIT;

/*falta ver*/
SELECT P1.x1,P1.y1,P1.x2,P1.y2,P2.x1,P2.y1,P2.x2,P2.y2
FROM region as P1, region as P2
WHERE P1.region.series_id = serieA AND P2.region.series_id = serieB;

SELECT compare_two_regions(P1.x1,P1.y1,P1.x2,P1.y2,P2.x1,P2.y1,P2.x2,P2.y2) into result;
return result;
end$$
DELIMITER ;

我收到以下错误：Not allowed to return a result set from a function

Answer 1

您可以尝试更改此

SELECT P1.x1,P1.y1,P1.x2,P1.y2,P2.x1,P2.y1,P2.x2,P2.y2
FROM region as P1, region as P2
WHERE P1.region.series_id = serieA AND P2.region.series_id = serieB;

SELECT compare_two_regions(P1.x1,P1.y1,P1.x2,P1.y2,P2.x1,P2.y1,P2.x2,P2.y2) into result;

到这个

SELECT compare_two_regions(P1.x1,P1.y1,P1.x2,P1.y2,P2.x1,P2.y1,P2.x2,P2.y2) into result
FROM region as P1, region as P2
WHERE P1.region.series_id = serieA AND P2.region.series_id = serieB;

如果查询结果返回多行，则会失败。如果要使用循环，则需要设置游标。