SQL PageRank实现

Question

那里有很好的SQL PageRank实现吗？我看过http://www.databasedevelop.com/197517/，但它缺少可读性和正确性（T-SQL）语法。

虽然我们在这，但有人知道上面的链接正在使用什么样的SQL？什么SQL使用'是'在随机的地方，'哪里'什么都没有，奇怪的AT关键字，等等？

Answer 1

根据您的SQL Server版本，可以查看OFFSET_FETCH窗口函数。这里有很多页面排名的应用程序。当然，这将需要2012年。

我也用SSIS和一个NTILE（）分割临时表来完成分页的能力，使用OFFSET_FETCH的缺席。通常使用类似记录计数除以我想在页面中看到的最大数量作为NTILE调用的种子。

无论出于何种原因，我甚至无法打开您的链接，所以希望这是您要求的。

MSDN - OFFSET_FETCH

MSDN - NTILE

Answer 2

我只是在SQL中实现的PageRank算法。该算法在以下进展中起作用。

1.计算PageRank初始等级值;

2.Joining 的PageRank表边缘表以发射秩值至邻接的节点，并且使用聚集函数总和为“收集”接收到的值。然后，将结果保存到寺庙表TmpRank;

交换的PageRank和的内容TmpRank，并转到步骤2，直到收敛条件被满足或达到最大重复时间。

下面是代码：

-- The graph data and algorithm source from the book "Mining of Massive Datasets", P175, http://infolab.stanford.edu/~ullman/mmds/book.pdf 
-- This script has been verified the correctness in SQL Server 2017 Linux Version. 
DROP TABLE Node; 
DROP TABLE Edge; 
DROP TABLE OutDegree; 
DROP TABLE PageRank; 
CREATE TABLE Node(id int PRIMARY KEY); 
CREATE TABLE Edge(src int,dst int, PRIMARY KEY (src, dst)); 
CREATE TABLE OutDegree(id int PRIMARY KEY, degree int); 
CREATE TABLE PageRank(id int PRIMARY KEY, rank float); 
CREATE TABLE TmpRank(id int PRIMARY KEY, rank float); 

--delete all records 
DELETE FROM Node; 
DELETE FROM Edge; 
DELETE FROM OutDegree; 
DELETE FROM PageRank; 
DELETE FROM TmpRank; 

--init basic tables 
INSERT INTO Node VALUES (0); 
INSERT INTO Node VALUES (1); 
INSERT INTO Node VALUES (2); 
INSERT INTO Node VALUES (3); 

INSERT INTO Edge VALUES (0, 1); 
INSERT INTO Edge VALUES (0, 2); 
INSERT INTO Edge VALUES (0, 3); 
INSERT INTO Edge VALUES (1, 0); 
INSERT INTO Edge VALUES (1, 3); 
INSERT INTO Edge VALUES (2, 2); 
INSERT INTO Edge VALUES (3, 1); 
INSERT INTO Edge VALUES (3, 2); 

--compute out-degree 
INSERT INTO OutDegree 
SELECT Node.id, COUNT(Edge.src) --Count(Edge.src) instead of Count(*) for count no out-degree edge 
FROM Node LEFT OUTER JOIN Edge 
ON Node.id = Edge.src 
GROUP BY Node.id; 

--WARN: There's no special process for node with out-degree, This may cause wrong result 
--  Please to make sure every node in graph has out-degree 

DECLARE @ALPHA float = 0.8; 
DECLARE @Node_Num int; 
SELECT @Node_Num = COUNT(*) FROM Node; 

--PageRank Init Value 
INSERT INTO PageRank 
SELECT Node.id, rank = (1 - @ALPHA)/@Node_Num 
FROM Node INNER JOIN OutDegree 
ON Node.id = OutDegree.id 

/* 
--For Debugging 
SELECT * FROM Node; 
SELECT * FROM Edge; 
SELECT * FROM OutDegree; 
SELECT * FROM PageRank; 
SELECT * FROM TmpRank; 
*/ 

DECLARE @Iteration int = 0; 

WHILE @Iteration < 50 
BEGIN 
--Iteration Style 
    SET @Iteration = @Iteration + 1 

    INSERT INTO TmpRank 
    SELECT Edge.dst, rank = SUM(@ALPHA * PageRank.rank/OutDegree.degree) + (1 - @ALPHA)/@Node_Num 
    FROM PageRank 
    INNER JOIN Edge ON PageRank.id = Edge.src 
    INNER JOIN OutDegree ON PageRank.id = OutDegree.id 
    GROUP BY Edge.dst 

    DELETE FROM PageRank; 
    INSERT INTO PageRank 
    SELECT * FROM TmpRank; 
    DELETE FROM TmpRank; 
END 

SELECT * FROM PageRank;