如何 select 行不是最近的并且与最后一个条目不同？

Question

如何 select 行不是最近的并且与上一个条目不同？我们通过上下文字段识别差异。

我的示例数据库：

CREATE TABLE duel (
    id int,
    title varchar(255),
    PRIMARY KEY (id)
);

CREATE TABLE try (
    id int,
    duel_id int,
    context varchar(255),
    recent tinyint(1),
    PRIMARY KEY (id),
    FOREIGN KEY (duel_id) REFERENCES duel(id)
);

INSERT INTO duel (id,title) VALUES (1,"1"),(2,"2"),(3,"3"),(4,"4");
    
INSERT INTO try (id,duel_id,context,recent) VALUES
    (1,1,"a",0),(2,1,"a",0),(3,1,"a",1),(4,2,"a",0),(5,2,"b",0),
    (6,2,"b",1),(7,3,"a",0),(8,3,"a",0),(9,3,"b",1),(10,4,"c",0),
    (11,4,"a",0),(12,4,"c",1);

我想从 try table 行中检索 ID：4、7、8 和 11。

我尝试了以下方法：

SELECT * FROM try
WHERE recent != 1 AND (SELECT context FROM try WHERE recent = 1) != context;

但是我遇到了以下错误：

ERROR 1242 (21000) at line 120: Subquery returns more than 1 row

不知道怎么处理。也许有子查询以外的解决方案？

Answer 1

您的问题的解决方案：（针对 MySQL 5.7）

SELECT id,duel_id,context,recent
FROM
(
SELECT *,
CASE 
WHEN @cntxt = context AND @did = duel_id AND recent = 0 THEN @cur
WHEN @cntxt = context AND @did = duel_id AND recent = 1 THEN (@cur := 1)
WHEN (@cntxt := context) IS NOT NULL AND (@did := duel_id) IS NOT NULL AND (@cur := recent) IS NOT NULL THEN recent
END as flag
FROM try, (SELECT @cur := 0, @cntxt := Null, @did := Null) r
ORDER BY duel_id, context,recent DESC
) as t
WHERE flag = 0
ORDER BY id;

db fiddle link

您的问题的解决方案：（针对 MySQL 8.0+）

WITH CT1 AS
(
SELECT *,
SUM(recent) OVER(PARTITION BY duel_id, context ORDER BY recent DESC) as rn
FROM try
)
SELECT id, duel_id, 
context, recent
FROM CT1
WHERE rn = 0
ORDER BY id;

dbfiddle link

如何 select 行不是最近的并且与最后一个条目不同？

How do I select rows that are not recent and are different from the last entry?

mysql

sql