Something I created to allow me to rapidly iterate on my data model in Excel and re-seed the database as I adjust it. Uses powershell and some assumptions on the format of the data to accomplish it.

Export-ExcelToSQL.ps1

Function Export-WorksheetToCSV
{
<#
.Synopsis
	This cmdlet converts .xlsx files to .csv.
.Description
	This cmdlet uses COM to open XLSX and then saves every tab as a separate CSV file. This only works if the
    individual tab CAN be converted to CSV.

    Ignores tabs named "_Ignore".
.Parameter Root
	The root directory where the files should be opened / saved to.
.Parameter FileBaseName
	The base filename without the extension.
.Example
	Export-WorksheetToCSV -Root "C:\ExcelFileDirectory\" -BaseFileName "TheFileToConvert"
	
    Opens the file at C:\ExcelFileDirectory\TheFileToConvert.xlsx and saves every tab as C:\ExcelFileDirectory\TheFileToConvert_(TabName).csv
#>
[CmdletBinding()]
Param(
[parameter(Mandatory=$true)]
[string]$Source, 
[parameter(Mandatory=$true)]
[string]$FileBaseName
)

    $excelFile = Join-Path $Source "$FileBaseName.xlsx"
    $E = New-Object -ComObject Excel.Application
    $E.Visible = $false
    $E.DisplayAlerts = $false
    $wb = $E.Workbooks.Open($excelFile)
    foreach ($ws in $wb.Worksheets)
    {
        if($ws.Name -notmatch "_Ignore") {
            $n = $FileBaseName + "_" + $ws.Name
            $savePath = Join-Path $root "$n.csv"
            $ws.SaveAs($savePath, 6)
        }
    }
    $E.Quit()
}

Function Export-CSVToSQL
{
<#
.Synopsis
	This cmdlet converts CSV files to Database Post-Deploy SQL Scripts.
.Description
	This cmdlet converts CSV files named like (schema).Data_*.csv to $schema.Seed.sql post-deploy scripts.

    CSV data must contain a header formatted like, e.g.:
        "Id","Name","Abbrev","_SeedScript"

    The Id field must be the unique id for the table. Columns named starting with "_" will be ignored when building
    the merge into script. The column named "_SeedScript" will be used to populate the seed data (required for now...).

.Parameter Source
	Required. The source directory in which the CSV files reside.
.Parameter Destination
	Required. The destination for the (schema).Seed.sql files.
.Parameter Schemas
	Required. A string array of schemas. Used to filter files and aggregate post-deploy scripts.
.Example
	Export-CSVToSQL -Root "C:\CsvFileDirectory\" -Destination "C:\TFS\Solution1\DatabaseProj\PostDeploy\" -Schemas "dbo","products"
	
    Opens the CSVs at C:\CsvFileDirectory\dbo.Data_*.csv and converts each (tab) into a table seed script. All "dbo" scripts will 
    be aggregated at C:\TFS\Solution1\DatabaseProj\PostDeploy\dbo.Seed.sql. The same thing will then occur for 
    C:\CsvFileDirectory\products.Data_*.csv which will be saved to C:\TFS\Solution1\DatabaseProj\PostDeploy\products.Seed.sql.
#>
[CmdletBinding()]
Param(
[parameter(Mandatory=$true)]
[string]$Source, 
[parameter(Mandatory=$true)]
[string]$Destination,
[parameter(Mandatory=$true)]
[string[]]$Schemas
)

    foreach($schema in $Schemas)
    {
        $files = Get-ChildItem $Source -Filter "$schema.Data_*.csv"
        $seedFileName = "$schema.Seed.sql"
        $seedFilePath = Join-Path "$Source" "$seedFileName"

        New-Item -path $Source -Name $seedFileName -Value 'USE [$(DatabaseName)]' -ItemType file -force
        Add-Content -Path $seedFilePath -Value "`r`nGO"
        Add-Content -Path $seedFilePath -Value "`r`nexec sp_msforeachtable 'ALTER TABLE ? NOCHECK CONSTRAINT all'`r`nGO"

        #Add-Content $source+$seedFileName ""

        foreach ($file in $files)
        {
            $csv = Import-Csv $file.FullName
            $linesInFile = 0
            $baseName = $file.BaseName.Split("_")[1]
            $content = @"
    
SET IDENTITY_INSERT [$schema].[$baseName] ON
GO

MERGE INTO [$schema].[$baseName] AS Target
USING (VALUES
"@
            foreach($row in $csv)
            {
                $content+="`r`n    "+$row._SeedScript
                $linesInFile++;
            }
            $content = $content.TrimEnd(",")+"`r`n)`r`n"
            $temp = ($csv[0].psobject.Properties | ? { $_.Name -notlike "_*" -and $_.Name -ne "Id" -and $_.MemberType -eq "NoteProperty" } | Select -ExpandProperty Name)
            $updateSetParams = New-Object object[] $temp.Length
            for($i=0; $i -lt $temp.Length; $i++)
            {
                $updateSetParams[$i] = ($temp[$i]) +" = Source."+($temp[$i])
            }
    
            $commaSeparatedHeaders =  "Id, "+($temp -join ", ")

            $content += "AS SOURCE ($commaSeparatedHeaders)`r`n"
            $content += "ON Target.Id = Source.Id`r`n"
            $content += "--update matched rows`r`n"
            $content += "WHEN MATCHED THEN`r`n"
            $content += "UPDATE SET " + ($updateSetParams -join ", ")+"`r`n"
            $content += "--insert new rows`r`n"
            $content += "WHEN NOT MATCHED BY TARGET THEN`r`n"
            $content += "INSERT ($commaSeparatedHeaders) VALUES ($commaSeparatedHeaders)`r`n"
            $content += "--delete rows that are in the target but not the source`r`n"
            $content += "WHEN NOT MATCHED BY SOURCE THEN`r`n"
            $content += "DELETE;`r`n`r`n"
            $content += "DBCC CHECKIDENT ('$schema.$baseName', RESEED, $linesInFile);`r`n`r`n"
            $content += "SET IDENTITY_INSERT [$schema].[$baseName] OFF`r`nGO"
    
            Add-Content -Path $seedFilePath -Value $content
        }

        Add-Content -Path $seedFilePath -Value "exec sp_msforeachtable 'ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all'`r`nGO"

        Copy-Item -Path $seedFilePath -Destination $Destination
    }

}

Function Export-ExcelToSql
{
<#
.Synopsis
	This cmdlet converts Excel files to Database Post-Deploy SQL Scripts.
.Description
	This cmdlet converts Excel files to CSV via Export-WorksheetToCSV and then to post-deploy sql scripts via Export-CSVToSQL.
.Parameter Source
	Required. The source directory in which the excel files reside.
.Parameter Destination
	Required. The destination for the (schema).Seed.sql files.
.Parameter Schemas
	Required. A string array of schemas. Used to filter files and aggregate post-deploy scripts.
.Example
	Export-CSVToSQL -Source "C:\CsvFileDirectory\" -Destination "C:\TFS\Solution1\DatabaseProj\PostDeploy\" -Schemas "dbo","products"
	
    Opens the CSVs at C:\CsvFileDirectory\dbo.Data_*.csv and converts each (tab) into a table seed script. All "dbo" scripts will 
    be aggregated at C:\TFS\Solution1\DatabaseProj\PostDeploy\dbo.Seed.sql. The same thing will then occur for 
    C:\CsvFileDirectory\products.Data_*.csv which will be saved to C:\TFS\Solution1\DatabaseProj\PostDeploy\products.Seed.sql.
#>
[CmdletBinding()]
Param(
[parameter(Mandatory=$true)]
[string]$Source, 
[parameter(Mandatory=$true)]
[string]$Destination, 
[parameter(Mandatory=$true)]
[string[]]$Schemas)

    $allSchemaCsvs = $schemas | % { Join-Path $Source "\$_.*.csv" }
    $allSQL = $schemas | % { Join-Path $Source "\$_.Seed.sql" }

    foreach ($schema in $Schemas)
    {
    
        #Remove-Item $allSchemaCsvs
    
        $files = Get-ChildItem $Source -Filter "$schema.Data.xlsx"#"*.Data.xlsx"

        foreach ($e in $files)
        {
            Export-WorksheetToCSV -root $Source -excelFileName $e.BaseName
        }

        Export-CSVToSQL -source $Source -destination $Destination -schemas $schema
    }
    $allSchemaCsvs | Remove-Item
    $allSQL | Remove-Item
}