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想象一下下面的Loans
表:
BorrowerID StartDate DueDate
=============================================
1 2012-09-02 2012-10-01
2 2012-10-05 2012-10-21
3 2012-11-07 2012-11-09
4 2012-12-01 2013-01-01
4 2012-12-01 2013-01-14
1 2012-12-20 2013-01-06
3 2013-01-07 2013-01-22
3 2013-01-15 2013-01-18
1 2013-02-20 2013-02-24
对于那些一次只借过一笔贷款的人,我该如何选择不同的 BorrowerID
?这包括只申请过一笔贷款的借款人,以及申请超过一笔贷款的借款人,前提是如果你要为他们的贷款划出一个时间表,那么这些贷款都不会重叠。例如,在上表中,它应该只找到借款人 1 和 2。
我尝试过将表连接到自身,但还没有真正成功。非常感谢任何指点!
最佳答案
要解决此问题,您需要采用两步方法,详细信息如下 SQL Fiddle 。我确实在示例数据中添加了一个 LoanId 列,并且查询要求存在这样一个唯一的 ID。如果没有,则需要调整连接子句以确保贷款不会与其自身匹配。
MS SQL Server 2008 架构设置:
CREATE TABLE dbo.Loans
(LoanID INT, [BorrowerID] int, [StartDate] datetime, [DueDate] datetime)
GO
INSERT INTO dbo.Loans
(LoanID, [BorrowerID], [StartDate], [DueDate])
VALUES
(1, 1, '2012-09-02 00:00:00', '2012-10-01 00:00:00'),
(2, 2, '2012-10-05 00:00:00', '2012-10-21 00:00:00'),
(3, 3, '2012-11-07 00:00:00', '2012-11-09 00:00:00'),
(4, 4, '2012-12-01 00:00:00', '2013-01-01 00:00:00'),
(5, 4, '2012-12-01 00:00:00', '2013-01-14 00:00:00'),
(6, 1, '2012-12-20 00:00:00', '2013-01-06 00:00:00'),
(7, 3, '2013-01-07 00:00:00', '2013-01-22 00:00:00'),
(8, 3, '2013-01-15 00:00:00', '2013-01-18 00:00:00'),
(9, 1, '2013-02-20 00:00:00', '2013-02-24 00:00:00')
GO
首先,您需要找出哪些贷款与另一笔贷款重叠。查询使用 <=
比较开始日期和截止日期。如果第二笔贷款在第一笔贷款结束的同一天开始,则该贷款将被视为重叠。如果您需要这些不重叠,请使用 <
相反,在这两个地方。
查询 1:
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L2.LoanID <> L1.LoanID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate)
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM dbo.Loans L1;
<强> Results :
| LOANID | BORROWERID | STARTDATE | DUEDATE | HASOVERLAPPINGLOAN |
|--------|------------|----------------------------------|---------------------------------|--------------------|
| 1 | 1 | September, 02 2012 00:00:00+0000 | October, 01 2012 00:00:00+0000 | 0 |
| 2 | 2 | October, 05 2012 00:00:00+0000 | October, 21 2012 00:00:00+0000 | 0 |
| 3 | 3 | November, 07 2012 00:00:00+0000 | November, 09 2012 00:00:00+0000 | 0 |
| 4 | 4 | December, 01 2012 00:00:00+0000 | January, 01 2013 00:00:00+0000 | 1 |
| 5 | 4 | December, 01 2012 00:00:00+0000 | January, 14 2013 00:00:00+0000 | 1 |
| 6 | 1 | December, 20 2012 00:00:00+0000 | January, 06 2013 00:00:00+0000 | 0 |
| 7 | 3 | January, 07 2013 00:00:00+0000 | January, 22 2013 00:00:00+0000 | 1 |
| 8 | 3 | January, 15 2013 00:00:00+0000 | January, 18 2013 00:00:00+0000 | 1 |
| 9 | 1 | February, 20 2013 00:00:00+0000 | February, 24 2013 00:00:00+0000 | 0 |
现在,利用该信息,您可以通过此查询确定没有重叠贷款的借款人:
查询 2:
WITH OverlappingLoans AS (
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L2.LoanID <> L1.LoanID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate)
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM dbo.Loans L1
),
OverlappingBorrower AS (
SELECT BorrowerID, MAX(HasOverlappingLoan) HasOverlappingLoan
FROM OverlappingLoans
GROUP BY BorrowerID
)
SELECT *
FROM OverlappingBorrower
WHERE hasOverlappingLoan = 0;
或者,您甚至可以通过计算贷款数量以及计算数据库中每个借款人与其他贷款重叠的贷款数量来获取更多信息。 (注意,如果贷款A和贷款B重叠,则该查询将两者都算作重叠贷款)
<强> Results :
| BORROWERID | HASOVERLAPPINGLOAN |
|------------|--------------------|
| 1 | 0 |
| 2 | 0 |
查询 3:
WITH OverlappingLoans AS (
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L2.LoanID <> L1.LoanID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate)
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM dbo.Loans L1
)
SELECT BorrowerID,COUNT(1) LoanCount, SUM(hasOverlappingLoan) OverlappingCount
FROM OverlappingLoans
GROUP BY BorrowerID;
<强> Results :
| BORROWERID | LOANCOUNT | OVERLAPPINGCOUNT |
|------------|-----------|------------------|
| 1 | 3 | 0 |
| 2 | 1 | 0 |
| 3 | 3 | 2 |
| 4 | 2 | 2 |
<小时/><小时/>
更新:由于该要求实际上需要一个不依赖于每笔贷款的唯一标识符的解决方案,因此我进行了以下更改:
1) 我添加了一个借款人,该借款人拥有两笔具有相同开始日期和到期日期的贷款
MS SQL Server 2008 架构设置:
CREATE TABLE dbo.Loans
([BorrowerID] int, [StartDate] datetime, [DueDate] datetime)
GO
INSERT INTO dbo.Loans
([BorrowerID], [StartDate], [DueDate])
VALUES
( 1, '2012-09-02 00:00:00', '2012-10-01 00:00:00'),
( 2, '2012-10-05 00:00:00', '2012-10-21 00:00:00'),
( 3, '2012-11-07 00:00:00', '2012-11-09 00:00:00'),
( 4, '2012-12-01 00:00:00', '2013-01-01 00:00:00'),
( 4, '2012-12-01 00:00:00', '2013-01-14 00:00:00'),
( 1, '2012-12-20 00:00:00', '2013-01-06 00:00:00'),
( 3, '2013-01-07 00:00:00', '2013-01-22 00:00:00'),
( 3, '2013-01-15 00:00:00', '2013-01-18 00:00:00'),
( 1, '2013-02-20 00:00:00', '2013-02-24 00:00:00'),
( 5, '2013-02-20 00:00:00', '2013-02-24 00:00:00'),
( 5, '2013-02-20 00:00:00', '2013-02-24 00:00:00')
GO
2) 这些“同等日期”贷款需要额外的步骤:
查询 1:
SELECT BorrowerID, StartDate, DueDate, COUNT(1) LoanCount
FROM dbo.Loans
GROUP BY BorrowerID, StartDate, DueDate;
<强> Results :
| BORROWERID | STARTDATE | DUEDATE | LOANCOUNT |
|------------|----------------------------------|---------------------------------|-----------|
| 1 | September, 02 2012 00:00:00+0000 | October, 01 2012 00:00:00+0000 | 1 |
| 1 | December, 20 2012 00:00:00+0000 | January, 06 2013 00:00:00+0000 | 1 |
| 1 | February, 20 2013 00:00:00+0000 | February, 24 2013 00:00:00+0000 | 1 |
| 2 | October, 05 2012 00:00:00+0000 | October, 21 2012 00:00:00+0000 | 1 |
| 3 | November, 07 2012 00:00:00+0000 | November, 09 2012 00:00:00+0000 | 1 |
| 3 | January, 07 2013 00:00:00+0000 | January, 22 2013 00:00:00+0000 | 1 |
| 3 | January, 15 2013 00:00:00+0000 | January, 18 2013 00:00:00+0000 | 1 |
| 4 | December, 01 2012 00:00:00+0000 | January, 01 2013 00:00:00+0000 | 1 |
| 4 | December, 01 2012 00:00:00+0000 | January, 14 2013 00:00:00+0000 | 1 |
| 5 | February, 20 2013 00:00:00+0000 | February, 24 2013 00:00:00+0000 | 2 |
3) 现在,由于每个贷款范围都是独一无二的,我们可以再次使用旧技术。然而,我们还需要考虑那些“同等日期”贷款。 (L1.StartDate <> L2.StartDate OR L1.DueDate <> L2.DueDate)
防止贷款与其自身匹配。 OR LoanCount > 1
考虑“同等日期”贷款。
查询 2:
WITH NormalizedLoans AS (
SELECT BorrowerID, StartDate, DueDate, COUNT(1) LoanCount
FROM dbo.Loans
GROUP BY BorrowerID, StartDate, DueDate
)
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate
AND (L1.StartDate <> L2.StartDate
OR L1.DueDate <> L2.DueDate)
)
OR LoanCount > 1
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM NormalizedLoans L1;
<强> Results :
| BORROWERID | STARTDATE | DUEDATE | LOANCOUNT | HASOVERLAPPINGLOAN |
|------------|----------------------------------|---------------------------------|-----------|--------------------|
| 1 | September, 02 2012 00:00:00+0000 | October, 01 2012 00:00:00+0000 | 1 | 0 |
| 1 | December, 20 2012 00:00:00+0000 | January, 06 2013 00:00:00+0000 | 1 | 0 |
| 1 | February, 20 2013 00:00:00+0000 | February, 24 2013 00:00:00+0000 | 1 | 0 |
| 2 | October, 05 2012 00:00:00+0000 | October, 21 2012 00:00:00+0000 | 1 | 0 |
| 3 | November, 07 2012 00:00:00+0000 | November, 09 2012 00:00:00+0000 | 1 | 0 |
| 3 | January, 07 2013 00:00:00+0000 | January, 22 2013 00:00:00+0000 | 1 | 1 |
| 3 | January, 15 2013 00:00:00+0000 | January, 18 2013 00:00:00+0000 | 1 | 1 |
| 4 | December, 01 2012 00:00:00+0000 | January, 01 2013 00:00:00+0000 | 1 | 1 |
| 4 | December, 01 2012 00:00:00+0000 | January, 14 2013 00:00:00+0000 | 1 | 1 |
| 5 | February, 20 2013 00:00:00+0000 | February, 24 2013 00:00:00+0000 | 2 | 1 |
此查询逻辑没有改变(除了切换开头)。
查询 3:
WITH NormalizedLoans AS (
SELECT BorrowerID, StartDate, DueDate, COUNT(1) LoanCount
FROM dbo.Loans
GROUP BY BorrowerID, StartDate, DueDate
),
OverlappingLoans AS (
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate
AND (L1.StartDate <> L2.StartDate
OR L1.DueDate <> L2.DueDate)
)
OR LoanCount > 1
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM NormalizedLoans L1
),
OverlappingBorrower AS (
SELECT BorrowerID, MAX(HasOverlappingLoan) HasOverlappingLoan
FROM OverlappingLoans
GROUP BY BorrowerID
)
SELECT *
FROM OverlappingBorrower
WHERE hasOverlappingLoan = 0;
<强> Results :
| BORROWERID | HASOVERLAPPINGLOAN |
|------------|--------------------|
| 1 | 0 |
| 2 | 0 |
4) 在此计数查询中,我们需要再次合并“同等日期”贷款计数。为此,我们使用 SUM(LoanCount)
而不是简单的 COUNT
。我们还必须乘以 hasOverlappingLoan
与 LoanCount 一起再次获得正确的重叠计数。
查询 4:
WITH NormalizedLoans AS (
SELECT BorrowerID, StartDate, DueDate, COUNT(1) LoanCount
FROM dbo.Loans
GROUP BY BorrowerID, StartDate, DueDate
),
OverlappingLoans AS (
SELECT
*,
CASE WHEN EXISTS(SELECT 1 FROM dbo.Loans L2
WHERE L2.BorrowerID = L1.BorrowerID
AND L1.StartDate <= L2.DueDate
AND L2.StartDate <= l1.DueDate
AND (L1.StartDate <> L2.StartDate
OR L1.DueDate <> L2.DueDate)
)
OR LoanCount > 1
THEN 1
ELSE 0
END AS HasOverlappingLoan
FROM NormalizedLoans L1
)
SELECT BorrowerID,SUM(LoanCount) LoanCount, SUM(hasOverlappingLoan*LoanCount) OverlappingCount
FROM OverlappingLoans
GROUP BY BorrowerID;
<强> Results :
| BORROWERID | LOANCOUNT | OVERLAPPINGCOUNT |
|------------|-----------|------------------|
| 1 | 3 | 0 |
| 2 | 1 | 0 |
| 3 | 3 | 2 |
| 4 | 2 | 2 |
| 5 | 2 | 2 |
我强烈建议找到一种方法来使用我的第一个解决方案,因为没有主键的贷款表是一种“奇怪”的设计。但是,如果您确实无法到达那里,请使用第二种解决方案。
关于sql - 选择没有日期范围重叠的行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19351019/
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