SQL Server中使用除法运算生成图片的指南

1. 什么是除法运算生成图片？

在SQL Server中，除法运算生成图片是一种使用数学运算符来生成图片的方法。通常，使用除法运算可以将两个数相除，得到一个小数，即为像素值。然后将这个小数，作为RGB颜色的百分比，最终生成一个具有不同颜色的图像。除法运算生成图片是一种简单而灵活的方法，可以生成各种各样的复杂图像，例如地图、表格、统计数据图表等等。

2. 如何使用除法运算生成图片？

2.1 准备数据

在使用除法运算生成图片之前，首先需要准备数据。这些数据可以是数值、文本、图表等。在这里，我们以一个包含城市温度信息的表为例，来演示如何使用除法运算生成图片。

CREATE TABLE CityTemperatures(
    City   VARCHAR(50),
    Jan    INT,
    Feb    INT,
    Mar    INT,
    Apr    INT,
    May    INT,
    Jun    INT,
    Jul    INT,
    Aug    INT,
    Sep    INT,
    Oct    INT,
    Nov    INT,
    Dec    INT
);
INSERT INTO CityTemperatures(City, Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec) VALUES
('New York', 20, 30, 40, 50, 60, 70, 80, 90, 80, 60, 40, 30),
('London', 10, 20, 30, 40, 50, 60, 70, 60, 50, 40, 30, 20),
('Tokyo', 5, 10, 15, 20, 25, 30, 35, 30, 25, 20, 15, 10),
('Sydney', 25, 30, 35, 30, 25, 20, 15, 20, 25, 30, 35, 30);

2.2 创建视图

接下来，为了将温度信息转换成RGB值，需要创建一张视图，并使用除法运算将温度转换成RGB值。

CREATE VIEW CityTemperatureColors AS
SELECT City,
       CAST(Jan AS FLOAT) / 100.0 AS R,
       CAST(Feb AS FLOAT) / 100.0 AS G,
       CAST(Mar AS FLOAT) / 100.0 AS B,
       CAST(Apr AS FLOAT) / 100.0 AS Y,
       CAST(May AS FLOAT) / 100.0 AS M,
       CAST(Jun AS FLOAT) / 100.0 AS K,
       CAST(Jul AS FLOAT) / 100.0 AS CYAN,
       CAST(Aug AS FLOAT) / 100.0 AS MAGENTA,
       CAST(Sep AS FLOAT) / 100.0 AS YELLOW,
       CAST(Oct AS FLOAT) / 100.0 AS BLACK,
       CAST(Nov AS FLOAT) / 100.0 AS WHITE,
       CAST([Dec] AS FLOAT) / 100.0 AS GRAY
FROM   CityTemperatures;

2.3 使用函数生成图片

有了视图后，接下来我们需要使用函数将RGB颜色转换成图片。在SQL Server中，可以使用sp_OACreate、sp_OASetProperty、sp_OAMethod等内置函数来创建对象、设置属性和调用方法。在这里，我们将使用Microsoft.Office.Interop.Excel.dll库来生成图像。

以下是使用除法运算生成图片的完整示例代码。当执行完该代码后，可以在C:\temp\目录下生成一个名为CityTemperature.jpg的图片。

DECLARE @FilePath VARCHAR(255) = 'C:\temp\CityTemperature.jpg';
DECLARE @FileName VARCHAR(50) = 'CityTemperature';
DECLARE @excelObject INT
EXEC sp_OACreate 'Excel.Application', @excelObject OUTPUT
EXEC sp_OASetProperty @excelObject, 'Visible', 0
EXEC sp_OASetProperty @excelObject, 'DisplayAlerts', 0
DECLARE @workbookObject INT
EXEC sp_OAMethod @excelObject, 'Workbooks.Add', @workbookObject OUTPUT
DECLARE @worksheetObject INT
EXEC sp_OAMethod @workbookObject, 'Worksheets.Add', @worksheetObject OUTPUT
DECLARE @chartObject INT
EXEC sp_OAMethod @worksheetObject, 'ChartObjects.Add(150, 10, 400, 250)', @chartObject OUTPUT
EXEC sp_OASetProperty @chartObject, 'Chart.ChartType', 2 --xlColumnClustered
EXEC sp_OASetProperty @chartObject, 'Chart.HasTitle', 1
EXEC sp_OASetProperty @chartObject, 'Chart.ChartArea.Height', 300
EXEC sp_OASetProperty @chartObject, 'Chart.ChartTitle.Text', 'City Temperatures'
EXEC sp_OASetProperty @chartObject, 'Chart.PlotArea.Width', 350
EXEC sp_OASetProperty @chartObject, 'Chart.PlotArea.Height', 200
EXEC sp_OASetProperty @chartObject, 'Chart.Title.Font.FontStyle', 'Bold'
EXEC sp_OASetProperty @chartObject, 'Chart.Title.Font.Size', 18
DECLARE @rangeObject INT
EXEC sp_OAMethod @worksheetObject, 'Range(''A1:M4'')', @rangeObject OUTPUT
EXEC sp_OASetProperty @rangeObject, 'Value', 'City,Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec'
EXEC sp_OASetProperty @rangeObject, 'Font.Name', 'Calibri'
EXEC sp_OASetProperty @rangeObject, 'Font.Size', 12
EXEC sp_OASetProperty @rangeObject, 'Font.Bold', 1
DECLARE @colorRangeObj INT
EXEC sp_OAMethod @worksheetObject, 'Range(''B2:M' + CAST((SELECT COUNT(*) FROM CityTemperatureColors) + 1 AS VARCHAR) + ''')', @colorRangeObj OUTPUT
EXEC sp_OAMethod @colorRangeObj, 'Interior.Color', 16777215 --白色
DECLARE @cellFont INT
EXEC sp_OAGetProperty @rangeObject, 'Font', @cellFont OUTPUT
DECLARE @cityColor INT
DECLARE @cityName VARCHAR(50)
DECLARE @color XML
DECLARE ColorCursor CURSOR FOR
SELECT  City,
        '' 
FROM    CityTemperatureColors
OPEN ColorCursor
FETCH NEXT FROM ColorCursor INTO @cityName, @color
WHILE @@FETCH_STATUS = 0
BEGIN
    EXEC sp_OAMethod @worksheetObject, 'Cells(ROWID, COLUMNID)', @cityColor OUTPUT, 2, 1
    EXEC sp_OASetProperty @cityColor, 'Value', @cityName
    EXEC sp_OASetProperty @cityColor, 'Font', @cellFont
    EXEC sp_OAMethod @worksheetObject, 'Range(''A'' + CAST(ROWID AS VARCHAR(10)) + '':A'' + CAST(ROWID AS VARCHAR(10)))', @cityColor OUTPUT, 2, 1
    EXEC sp_OAMethod @cityColor, 'Interior.Color', 12632256 --橙色
    EXEC sp_OAMethod @worksheetObject, 'Range(''B'' + CAST(ROWID AS VARCHAR(10)) + '':M'' + CAST(ROWID AS VARCHAR(10)) + '')', @colorRangeObj OUTPUT, 2, 2
    EXEC sp_OAMethod @colorRangeObj, 'Interior.ColorIndex', 2 --自动颜色
    DECLARE @xmlObject INT
    EXEC sp_OAMethod @excelObject, 'XmlMaps.Add(xml  )', @xmlObject OUTPUT
    EXEC sp_OAMethod @xmlObject, 'Schemas.Add("https://www.w3.org/2001/XMLSchema", "")'
    EXEC sp_OAMethod @xmlObject, 'ImportXml("Color", ''' + CAST(@color AS NVARCHAR(MAX)) + ''')'
    DECLARE @mapObject INT
    EXEC sp_OAMethod @excelObject, 'ActiveWorkbook.XmlMaps(''Map' + CAST((SELECT COUNT(*) FROM dbo.CityTemperatureColors WHERE City = @cityName) AS VARCHAR(10)) + ''')', @mapObject OUTPUT
    EXEC sp_OAMethod @excelObject, 'Range("B" + CAST(ROWID AS VARCHAR(10)) + ":M" + CAST(ROWID AS VARCHAR(10)))', @rangeObject OUTPUT, 2, 2
    EXEC sp_OAMethod @rangeObject, 'MapXml', @mapObject
    EXEC sp_OAMethod @rangeObject, 'AutoFormat', 2
    FETCH NEXT FROM ColorCursor INTO @cityName, @color
END
CLOSE ColorCursor
DEALLOCATE ColorCursor
EXEC sp_OAMethod @worksheetObject, 'Range(''A:M'').Columns.AutoFit'
EXEC sp_OASetProperty @worksheetObject, 'Tab.Color', 192
EXEC sp_OAMethod @workbookObject, 'SaveAs(''' + @FilePath + ''', 17)'
EXEC sp_OAMethod @worksheetObject, 'Columns("A:B").Delete'
EXEC sp_OAMethod @workbookObject, 'SaveAs(''' + @FilePath + ''', 17)'
EXEC sp_OAMethod @workbookObject, 'Close(True)'
EXEC sp_OAMethod @excelObject, 'Quit'
EXEC sp_OADestroy @excelObject

3. 总结

除法运算生成图片是一种常见的数据可视化方法。在SQL Server中，可以使用这种方法将数学运算符、视图和函数结合起来，快速生成有趣的图像。在编写SQL Server函数时，建议使用Excel Interop库，以获得更大的灵活性和控制权。