SQL扫描数据库中的先前记录

Question

考虑表

          Index    Col_1    Col_2   Value_of_Interest
Record_1    1
Record_2    2
   .
   .
   .
Record_N    N

我想选择一组记录{Record_i}，Col_1

中存在Record_i+1 {SELECT Col_2 FROM table WHERE Index<i}个 Index Col_1 Col_2 Value_of_Interest Record_1 1 Ed Bill 1 Record_2 2 James Rob 0 Record_3 3 Tom Rob 1 Record_4 4 Bill Rob 0

例如，考虑表

          Index    Col_1    Col_2   Value_of_Interest
Record_3    3       Tom     Rob            1

查询将返回

Col_1

Record_4的{​​{1}}为Bill，并且包含在之前记录的Col_2中。

是否可以编写执行此操作的SQL查询？

Answer 1

SELECT *
FROM MyTable AS T1
WHERE (SELECT Col_1
       FROM MyTable AS T2
       WHERE T2.Index = T1.Index + 1
      ) IN (SELECT Col_2
            FROM MyTable AS T3
            WHERE T3.Index < T1.Index)

Answer 2

SQL Fiddle

MySQL 5.5.32架构设置：

CREATE TABLE Table1
    (`Index` int, `Col_1` varchar(5), `Col_2` varchar(4), `Value_of_Interest` int)
;

INSERT INTO Table1
    (`Index`, `Col_1`, `Col_2`, `Value_of_Interest`)
VALUES
    (1, 'Ed', 'Bill', 1),
    (2, 'James', 'Rob', 0),
    (3, 'Tom', 'Rob', 1),
    (4, 'Bill', 'Rob', 0)
;

查询1 ：

SELECT t1.`Index`, t1.Col_1, t1.Col_2, t1.Value_of_Interest
FROM Table1 t1
WHERE t1.`index` =
(SELECT t2.`index`-1
FROM Table1 t2
WHERE t2.Col_1 IN 
     (SELECT Col_2 FROM Table1 t3 WHERE t3.`Index` < t2.`Index`))

<强> Results ：

| INDEX | COL_1 | COL_2 | VALUE_OF_INTEREST |
|-------|-------|-------|-------------------|
|     3 |   Tom |   Rob |                 1 |