HSQL SELECT 语句不工作

Question

我是 HSQL 新手。尝试了如下程序；

CREATE PROCEDURE GetData(ObjectId VARCHAR(36)) READS SQL DATA 
DYNAMIC RESULT SETS 1
BEGIN ATOMIC
    DECLARE MaxVal NUMERIC(19,2);
    DECLARE MinVal NUMERIC(19,2);
    DECLARE BiggestObjectName VARCHAR(50);
    DECLARE SmallestObjectName VARCHAR(50);

    SET MaxVal = (SELECT MAX(HeightValue) FROM ObjectData WHERE ObjectId=ObjectId);
    SET MinVal = (SELECT MIN(HeightValue) FROM ObjectData WHERE ObjectId=ObjectId);
    SET BiggestObjectName = (SELECT ObjectName FROM ObjectData WHERE ObjectId=ObjectId AND HeightValue=MaxVal);
    SET SmallestObjectName = (SELECT ObjectName FROM ObjectData WHERE ObjectId=ObjectId AND HeightValue=MinVal);

  if MaxVal IS NOT NULL THEN
    DECLARE result CURSOR WITH RETURN FOR
        SELECT MaxVal AS MaximumHeight, MinVal AS MinimumHeight, BiggestObjectName AS LargestDisplayCaseName, SmallestObjectName AS SmallestDisplayCaseName FOR READ ONLY;
  OPEN result;
END

但是我得到错误；

Caused by: java.sql.SQLSyntaxErrorException: unexpected token: ; required: INTO

语法不正确吗？

感谢任何帮助:)

Answer 1

您没有使用正确的语法来创建过程。根据语法，您必须将从 table 中选择的值放入局部变量中。按照下面的例子。

CREATE PROCEDURE get_customer(IN id INT, OUT firstname VARCHAR(50), OUT lastname VARCHAR(50)) 
    READS SQL DATA
    BEGIN ATOMIC
    -- this statement uses the id to get firstname and lastname
    SELECT first_name, last_name INTO firstname, lastname FROM customers WHERE cust_id = id;
END

希望对你有所帮助

Answer 2

您的存储过程有几处错误。首先，我认为您不能 declare 游标作为 IF 语句的一部分。

变量的赋值需要使用 select ... into 或者您需要将 select 语句放在括号中：

SET MaxVal = (SELECT MAX(HeightValue) FROM ObjectData WHERE ObjectId=ObjectId);
SET ObjectName = (SELECT ObjectName FROM ObjectData WHERE ObjectId=ObjectId AND HeightValue=MaxVal);

或

SELECT MAX(HeightValue) 
  into maxval
FROM ObjectData 
WHERE ObjectId=ObjectId;

您也不能使用 = 或 <> 来比较 NULL 值。 if MaxVal != NULL THEN 需要

if maxval is not null then 
   ...
end if; --<< you also forgot the `end if`

你也不能在没有 FROM 子句的情况下使用 SELECT 语句，而且我认为你不能定义一个只有 selects 来自变量的值的游标数据库。

但是不需要中间的 selects，你可以在一个 select:

中完成

CREATE PROCEDURE GetData(ObjectId VARCHAR(36)) READS SQL DATA 
DYNAMIC RESULT SETS 1
BEGIN ATOMIC

  DECLARE result CURSOR FOR
    select o1.heightvalue as maximumheight, o1.objectname as displaycasename
    from objectdata o1
    where objectid = 'one' 
    and heightvalue = (select max(heightvalue) 
                       from objectdata o2 
                       where o2.objectid = o1.objectid);

  OPEN result;

END;

HSQL SELECT 语句不工作

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