Get Sitecore blob item and save it as a file

SitecoreDownloadFileFromDB.ps1

$itemId = '--Your Item id--'
$fieldId = '{40E50ED9-BA07-4702-992E-A912738D32DC}' #blob field id. Please change as per requirement if required. 
$outputFile = 'd:\custom.js' #file path to save
 
# SQL connection
$connectionString = "--your connection string--"
$query = @"
DECLARE @ItemId UNIQUEIDENTIFIER = '$itemId';
DECLARE @BlobFieldId UNIQUEIDENTIFIER = '$fieldId';
DECLARE @BlobId UNIQUEIDENTIFIER;
 
SELECT 
    @BlobId = CAST(Value AS UNIQUEIDENTIFIER)
FROM 
    [dbo].[Fields]
WHERE 
    ItemId = @ItemId AND FieldId = @BlobFieldId;
 
SELECT Data FROM [dbo].[Blobs] WHERE BlobId = @BlobId;
"@
 
# Run SQL query
$connection = New-Object System.Data.SqlClient.SqlConnection $connectionString
$command = $connection.CreateCommand()
$command.CommandText = $query
$connection.Open()
$reader = $command.ExecuteReader()
if ($reader.Read()) {
    $buffer = New-Object byte[] $reader.GetBytes(0, 0, $null, 0, 0)
    $reader.GetBytes(0, 0, $buffer, 0, $buffer.Length)
    [IO.File]::WriteAllBytes($outputFile, $buffer)
}
$connection.Close()