复杂 SQL 计数查询

Question

您好，我的作业被一个 SQL 查询卡住了，希望能得到一些帮助。

我需要获取执行效果最好的项目的项目 ID - (VERY_GOOD 记录数 + GOOD 记录数) - (VERY_BAD 记录数 + BAD 记录数) 最大的项目

我在数据库 (HSQLDB) 中的架构和测试记录

CREATE TABLE
    PROJECT
    (
        ID IDENTITY NOT NULL PRIMARY KEY,
        PROJECT_NAME VARCHAR(255) NOT NULL
    );

CREATE TABLE
    RECORD
    (
        ID IDENTITY NOT NULL PRIMARY KEY,
        RESULT VARCHAR(255) NOT NULL,
    );

CREATE TABLE
    RECORD_PROJECT
    (
        PROJECT_ID INTEGER NOT NULL,
        RECORD_ID INTEGER NOT NULL,
        PRIMARY KEY(PROJECT_ID, RECORD_ID),
        FOREIGN KEY (PROJECT_ID) REFERENCES PROJECT(ID) ON DELETE CASCADE,
        FOREIGN KEY (RECORD_ID) REFERENCES RECORD(ID)
    );  

以及测试数据：

INSERT INTO PROJECT (PROJECT_NAME) VALUES ('Bake a cake');
INSERT INTO PROJECT (PROJECT_NAME) VALUES ('Clean the house');

INSERT INTO RECORD (RESULT) VALUES ('GOOD');
INSERT INTO RECORD (RESULT) VALUES ('VERY_GOOD');
INSERT INTO RECORD (RESULT) VALUES ('VERY_GOOD');
INSERT INTO RECORD (RESULT) VALUES ('BAD');
INSERT INTO RECORD (RESULT) VALUES ('VERY_BAD');

INSERT INTO RECORD_PROJECT (PROJECT_ID, RECORD_ID) VALUES (0,0);
INSERT INTO RECORD_PROJECT (PROJECT_ID, RECORD_ID) VALUES (1,1);
INSERT INTO RECORD_PROJECT (PROJECT_ID, RECORD_ID) VALUES (1,2);
INSERT INTO RECORD_PROJECT (PROJECT_ID, RECORD_ID) VALUES (0,3);
INSERT INTO RECORD_PROJECT (PROJECT_ID, RECORD_ID) VALUES (1,4);

（我从表格中删除了不相关的字段）

因此，有了这些数据，我有 3 条好记录和 2 条坏记录，我需要获得“评级”最高的项目，根据目前的情况，这将是 Clean the house其他项目的 3 个好评超过 2 个差评。

也许有人会解决这个问题，谢谢！

Answer 1

这应该是 MySQL-Dialect 中的（不是 testet）SQL：

SELECT rp.PROJECT_ID, p.PROJECT_NAME
   SUM(CASE WHEN rp.RECORD_ID < 3 THEN 1 ELSE 0 END) AS rating
FROM RECORD_PROJEKT AS rp
JOIN PROJECT AS p ON p.ID = rp.PROJECT_ID
GROUP BY rp.PROJECT_ID
ORDER BY rating DESC