F# store data in ms access table - f#

Question

how can i export arrays to ms access table using OleDbConnection. Below is the code i have so far.
let A=y|>Array.map (fun x->x.a)
let B=y|>Array.map (fun x->x.b)
let C=y|>Array.map (fun x->x.c)
let D=y|>Array.map (fun x->x.d)
let cnn = #"Provider=Microsoft.ACE.OLEDB.12.0;
Data Source=U:\test.accdb;
Persist Security Info=False;"
let conn = new OleDbConnection(cnn)
conn.Open()
use com = conn.CreateCommand()
com.CommandText <- "INSERT INTO Test values" {A,B,C,D}
com.ExecuteNonQuery() |> ignore
conn.Close()

Answer 1

In order to insert multiple rows, you need to issue multiple commands. Access doesn't allow inserting multiple values with one insert statement, see this question for more: Insert multiple rows using one insert statement in Access 2010
As long as you're fine with using multiple statements, you have to prepare the command correctly - that is, include the actual values after the VALUES part. And while you're at it, you should use parameters, too, if you don't want to be vulnerable to SQL injection. Like this:
use com = conn.CreateCommand()
com.CommandText <- "INSERT INTO Test values( ?, ?, ?, ? )"
let param name =
let p = com.CreateParameter()
p.ParameterName <- name
com.Parameters.Add p
p
let pA, pB, pC, pD = param "#a", param "#b", param "#c", param "#d"
y |> Array.iter (fun x ->
pA.Value <- x.a
pB.Value <- x.b
pC.Value <- x.c
pD.Value <- x.d
com.ExecuteNonQuery() )
conn.Close()
If you really want to speed it up, you'll have to find a way to bulk-insert records into Access, similar to SqlBulkInsert for SQL server. I don't know of such way, if it even exists.
Alternatively, you can create a commands consisting of N insert statements (where N = y.Length), but then that statement will have 4N parameters, and I believe Access had a limitation on the number of parameters.
Alternatively-alternatively, you can do the above, but without parameters, inserting values right into the text of the SQL command:
let commandText =
y
|> Seq.map (fun x ->
// assuming all four parameters are strings
sprintf "INSERT INTO Test values( '%s', '%s', '%s', '%s' )" x.a x.b x.c x.d
|> String.concat " "
use com = conn.CreateCommand()
com.CommandText <- commandText
com.ExecuteNonQuery()
conn.Close()
But in that case, you open yourself up to SQL injection attacks. You'll have to sanitize your array values very carefully to prevent it. I do not recommend doing this just to gain a few extra seconds in performance.
And speaking of performance: are you absolutely sure multiple insert statements are going to be too slow for your purposes? Why? Have you measured it? How?
Remember the golden rule of performance tuning: first measure, then optimize.