Tidying up a powershell script - powershell

Question

So I need help tidying up a script that I have. The purpose of this script is to make 18 different sql files based on the data below 18 different column headers. What my script does now is make 1 sql file based on which column I choose to input via "Read-Host". This is my current script
function get-header
{Read-Host "Type the Column header betwen B-Z for which sql files needs to be created"
}
function get-column
{
Read-Host "Type the Column number"
}
do
{
$val = get-header
}
while(!($val))
do
{$col = get-column
}
while(!($col))
switch ($val)
{
"B"{$column = "1"}
"C"{$column = "2"}
"D"{$column = "3"}
"E"{$column = "4"}
"F"{$column = "5"}
"G"{$column = "6"}
"H"{$column = "7"}
"I"{$column = "8"}
"J"{$column = "9"}
"K"{$column = "10"}
"L"{$column = "11"}
"M"{$column = "12"}
"N"{$column = "13"}
"O"{$column = "14"}
"P"{$column = "15"}
"Q"{$column = "16"}
"R"{$column = "17"}
"S"{$column = "18"}
"T"{$column = "19"}
"U"{$column = "20"}
"V"{$column = "21"}
"W"{$column = "22"}
"X"{$column = "23"}
"Y"{$column = "24"}
"Z"{$column = "25"}
default { $column = 'Unknown' }
}
if ($column -eq 'Unknown')
{
Write-Warning "Not a valid input"
return
}
$csv = Import-Csv "Indices Updates - September 2018.csv" -Header 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26
$date = (Get-Date -Format "MM/dd/yyyy").Replace("-","/")
$sql = #("INSERT INTO benchmark_values(created_at,benchmark_id,date,amount,created_by_username)
foreach($data in $csv)
{
$secondcolumn = [int]$column + 1
$sql += "('$date',$col,'$($data.1)',$($data.$secondcolumn),'BPylla'),"
}
$sql | Out-File "sqldata.sql"
Now I want to get rid of read-host entirely because I dont want to input any values. I also will give an example of what the csv file looks like and what the sql file should look like.
So the goal is to produce different sql files from each column of information using the the sql format posted. I already have the template for that in my script now, I just need the script to create all the sql files based on headers and still input the data below the headers in the new sql files. Any help would be greatly appreciated! Thanks!