MySQL的函數創建語句拋出錯誤

Question

CREATE FUNCTION INPolygon(pnt varchar(50),poly varchar(500)) RETURNS int(1) 
    DETERMINISTIC 
BEGIN 
DECLARE x, y, p1x, p1y, p2x, p2y float(20, 16) DEFAULT 0; 
DECLARE counter,i INT DEFAULT 1; 
DECLARE touches float(20,16); 
DECLARE intersect int DEFAULT 0; 
set counter = substrCount(poly,"#") + 1; 
set x = trim(strSplit(pnt,',',1)); 
set y = trim(strSplit(pnt,',',2)); 
while i <= counter DO 
set p1x = strSplit(strSplit(poly,'#',i), ',', 1); 
set p1y = strSplit(strSplit(poly,'#',i), ',', 2); 
set p2x = strSplit(strSplit(poly, '#', i+1), ',', 1); 
set p2y = strSplit(strSplit(poly, '#', i+1), ',', 2); 
IF ((x = p1x AND y = p1y) OR (x = p2x AND y = p2y)) THEN 
RETURN 1; 
END IF; 
IF (p1y = p2y and p1y = y and x > MIN(p1x, p2x) and x < MAX(p1x, p2x)) THEN 
return 1; 
END IF; 
IF (y > MIN(p1y, p2y) AND y <= MAX(p1y,p2y) AND x <= MAX(p1x, p2x) AND p1y != p2y) THEN 
set touches = (y - p1y) * (x - p1x)/(p2y - p1y) + x; 
IF touches = x THEN 
return 1; 
END IF; 
IF p1x = p2x OR x <= touches THEN 
set intersect = intersect+1; 
END IF; 
END IF; 
END WHILE; 
RETURN intersect % 2; 
END 

我拋出一個錯誤說

您的SQL語法錯誤;檢查與您的MySQL服務器版本相對應的手冊，以在'p2x'附近使用正確的語法並且x < MAX（p1x，p2x））然後返回1;萬一; IF（Y> MIN（P1Y，P2Y）和y」的線19

Answer 1

不能使用min()和max()這樣的。使用LEAST()和GREATEST()拿到2列的最低和最高值。更改在您使用MIN()從

MIN(p1y, p2y) 

到

LEAST(p1y, p2x) 

和

段

MAX(p1y, p2y) 

到

GREATEST(p1y, p2y)