在 Oracle 11g 中计数

Question

我整天都在与 oracle 练习作斗争，但我又一次陷入困境。我需要 select 拳击手的姓氏以及他们在每个重量类别中的胜利。

所以我有：

table "boxer" 列：id、fname、lname、weight
table "fight" 带有来自 table 拳击手的两个外键（id_boxer1 和 id_boxer2）和一个列获胜者（如果 boxer1 获胜则获胜者将是 1 号，如果 boxer2 获胜则获胜者将是 2 号）
table "category_weight" 列：id，min_weight，max_weight，名称（类别）

示例：

CREATE TABLE category_weight(
    id    INTEGER NOT NULL,
    min_weight          SMALLINT NOT NULL,
    max_weight          SMALLINT NOT NULL,
    name  VARCHAR2(20) NOT NULL
);

ALTER TABLE category_weight ADD CONSTRAINT category_weight_pk PRIMARY KEY ( id );

CREATE TABLE boxer(
    id  INTEGER NOT NULL,
    fname       VARCHAR2(20) NOT NULL,
    lname      VARCHAR2(20) NOT NULL,
    weight     INTEGER NOT NULL
);

ALTER TABLE boxer ADD CONSTRAINT boxer_pk PRIMARY KEY ( id );

CREATE TABLE fight(
    id       INTEGER NOT NULL,
    winner SMALLINT NOT NULL,
    id_category_weight  INTEGER NOT NULL,
    id_boxer1     INTEGER NOT NULL,
    id_boxer2     INTEGER NOT NULL
);

ALTER TABLE fight ADD CONSTRAINT fight_pk PRIMARY KEY ( id );

ALTER TABLE fight
    ADD CONSTRAINT boxer_fk FOREIGN KEY ( id_boxer1 )
        REFERENCES boxer ( id );

ALTER TABLE fight
    ADD CONSTRAINT boxer_fk2 FOREIGN KEY ( id_boxer2 )
        REFERENCES boxer ( id );

ALTER TABLE fight
    ADD CONSTRAINT categ_weight_fk FOREIGN KEY ( id_category_weight )
        REFERENCES category_weight ( id );

INSERT INTO boxer
VALUES ('1', 'Johnny','Johnny','60');
INSERT INTO boxer
VALUES ('2', 'Anthonny','Anthonny','54');
INSERT INTO boxer
VALUES ('3', 'Anonimm','Anonimm','59');
INSERT INTO boxer
VALUES ('4', 'John','Johnowski','71');

INSERT INTO category_weight
VALUES ('1', '1','70','category1');
INSERT INTO category_weight
VALUES ('2', '71','100','category2');

INSERT INTO fight
VALUES ('1','1','1','1','2');
INSERT INTO fight
VALUES ('2','2','1','3','1');

ID为“1”的拳击手在类别1中赢得了两场比赛，因此结果应该是：

Lname          Category       Wins
Johnny         category1      2

Answer 1

在这里，试试这个：

SELECT b.lname, 
       cw.max_weight AS WEIGHT_CLASS,
       COUNT(CASE WHEN f.winner = b.id THEN 1 ELSE NULL END) AS WINS
FROM boxer b
INNER JOIN fight f ON b.id = f.id_boxer1 OR b.id = f.id_boxer2
INNER JOIN category_weight cw ON f.id_category_weight = cw.id
GROUP BY b.lname, cw.max_weight

在 Oracle 11g 中计数

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