根据“坐标”生成趋势图

数据库环境：SQL SERVER 2008R2

　　有一“坐标”表t，表结构如下：

　　id           int，

　　num       int

　　字段id是序号，递增且连续，字段num是数值类型。id可以看成是坐标轴的横轴，num则跟纵轴有关系，

连续的2行记录，如果后一行的num值比前一行的num值大，则是递增趋势，反之，是递减趋势。要实现的效果如下图1：

　　实现思路：

　　将id=1的“坐标”所在纵轴设定为0，然后遍历后续所有的“坐标”，后面“坐标”的num值比前一个“坐标”的num大的，则纵坐标+1，

否则纵坐标-1。再对整理后的结果集进行行转列，根据纵坐标分组。

1.建表，插入测试数据

CREATE TABLE t(id INT,num INT)
INSERT INTO t VALUES(1,1);
INSERT INTO t VALUES(2,3);
INSERT INTO t VALUES(3,4);
INSERT INTO t VALUES(4,7);
INSERT INTO t VALUES(5,5);
INSERT INTO t VALUES(6,2);
INSERT INTO t VALUES(7,6);
INSERT INTO t VALUES(8,8);
INSERT INTO t VALUES(9,4);
INSERT INTO t VALUES(10,0);
INSERT INTO t VALUES(11,9);
INSERT INTO t VALUES(12,10);
INSERT INTO t VALUES(13,12);
INSERT INTO t VALUES(14,11);
INSERT INTO t VALUES(15,17);
INSERT INTO t VALUES(16,4);
INSERT INTO t VALUES(17,2);
INSERT INTO t VALUES(18,1);

2.遍历所有“坐标”，生成分组依据

WITH x1 ( id, num, gp )AS ( SELECT   id ,num ,0 AS gpFROM     t x0WHERE    id = 1UNION ALLSELECT   x0.id ,x0.num ,CASE WHEN x0.num > x1.num THEN x1.gp - 1ELSE x1.gp + 1END AS gpFROM     t x0 ,x1WHERE    x0.id = x1.id + 1)

3.行转列实现最终结果集

SELECT  ISNULL(CAST([1] AS VARCHAR(2)), '') [1] ,ISNULL(CAST([2] AS VARCHAR(2)), '') [2] ,ISNULL(CAST([3] AS VARCHAR(2)), '') [3] ,ISNULL(CAST([4] AS VARCHAR(2)), '') [4] ,ISNULL(CAST([5] AS VARCHAR(2)), '') [5] ,ISNULL(CAST([6] AS VARCHAR(2)), '') [6] ,ISNULL(CAST([7] AS VARCHAR(2)), '') [7] ,ISNULL(CAST([8] AS VARCHAR(2)), '') [8] ,ISNULL(CAST([9] AS VARCHAR(2)), '') [9] ,ISNULL(CAST([10] AS VARCHAR(2)), '') [10] ,ISNULL(CAST([11] AS VARCHAR(2)), '') [11] ,ISNULL(CAST([12] AS VARCHAR(2)), '') [12] ,ISNULL(CAST([13] AS VARCHAR(2)), '') [13] ,ISNULL(CAST([14] AS VARCHAR(2)), '') [14] ,ISNULL(CAST([15] AS VARCHAR(2)), '') [15] ,ISNULL(CAST([16] AS VARCHAR(2)), '') [16] ,ISNULL(CAST([17] AS VARCHAR(2)), '') [17] ,ISNULL(CAST([18] AS VARCHAR(2)), '') [18]FROM    ( SELECT    *FROM      x1) AS t1 PIVOT( MAX(num) FOR id IN ( [1], [2], [3], [4], [5], [6],[7], [8], [9], [10], [11],[12], [13], [14], [15], [16],[17], [18] ) )AS t2

　　如果要实现比较逼真的趋势图，用“/”、“”替代数值，实现下图2的效果，只需在遍历坐标的时候再做些处理即可。

　　实现的SQL脚本：

WITH    x1 ( id, num, cc, gp )AS ( SELECT   id ,num ,'/' AS cc ,0 AS gpFROM     t x0WHERE    id = 1UNION ALLSELECT   x0.id ,x0.num ,CASE WHEN x0.num > x1.num THEN '/'ELSE ''END AS cc ,CASE WHEN x0.num > x1.num THEN x1.gp - 1ELSE x1.gp + 1END AS gpFROM     t x0 ,x1WHERE    x0.id = x1.id + 1)SELECT  ISNULL([1], '') [1] ,ISNULL([2], '') [2] ,ISNULL([3], '') [3] ,ISNULL([4], '') [4] ,ISNULL([5], '') [5] ,ISNULL([6], '') [6] ,ISNULL([7], '') [7] ,ISNULL([8], '') [8] ,ISNULL([9], '') [9] ,ISNULL([10], '') [10] ,ISNULL([11], '') [11] ,ISNULL([12], '') [12] ,ISNULL([13], '') [13] ,ISNULL([14], '') [14] ,ISNULL([15], '') [15] ,ISNULL([16], '') [16] ,ISNULL([17], '') [17] ,ISNULL([18], '') [18]FROM    ( SELECT    id ,cc ,gpFROM      x1) AS t1 PIVOT( MAX(cc) FOR id IN ( [1], [2], [3], [4], [5], [6],[7], [8], [9], [10], [11], [12],[13], [14], [15], [16], [17],[18] ) )AS t2