我在尝试创建此存储过程时遇到了一些困难,欢迎提供任何帮助:
create procedure checando(in nombrecillo varchar(30), in contrilla varchar(30), out resultado int)
begin
if exists (select * from compas where nombre = nombrecillo and contrasenia = contrilla) then
set resultado = 0;
else if exists (select * from compas where nombre = nombrecillo) then
set resultado = -1;
else
set resultado = -2;
end if;
end;
我正在研究的表是:
+-------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| Nombre | varchar(30) | YES | | NULL | |
| contrasenia | varchar(30) | YES | | NULL | |
+-------------+-------------+------+-----+---------+-------+
答案 0 :(得分:30)
问题是您未关闭if
或者您需要elseif
:
create procedure checando(
in nombrecillo varchar(30),
in contrilla varchar(30),
out resultado int)
begin
if exists (select * from compas where nombre = nombrecillo and contrasenia = contrilla) then
set resultado = 0;
elseif exists (select * from compas where nombre = nombrecillo) then
set resultado = -1;
else
set resultado = -2;
end if;
end;
答案 1 :(得分:16)
我认为这个结构:if exists (select...
特定于MS SQL。在MySQL EXISTS
谓词中告诉您子查询是否找到任何行,并且它是这样使用的:SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2);
您可以像这样重写上面的代码行:
DELIMITER $$
CREATE PROCEDURE `checando`(in nombrecillo varchar(30), in contrilla varchar(30), out resultado int)
BEGIN
DECLARE count_prim INT;
DECLARE count_sec INT;
SELECT COUNT(*) INTO count_prim FROM compas WHERE nombre = nombrecillo AND contrasenia = contrilla;
SELECT COUNT(*) INTO count_sec FROM FROM compas WHERE nombre = nombrecillo;
if (count_prim > 0) then
set resultado = 0;
elseif (count_sec > 0) then
set resultado = -1;
else
set resultado = -2;
end if;
SELECT resultado;
END
答案 2 :(得分:1)
您可以使用CASE
WHEN
,如同IF
ELSE
一样。
SELECT FROM A a
LEFT JOIN B b
ON a.col1 = b.col1
AND (CASE
WHEN a.col2 like '0%' then TRIM(LEADING '0' FROM a.col2)
ELSE substring(a.col2,1,2)
END
)=b.col2;
p.s:以防有人需要这种方式。