Executing queries

To execute query, open connection to a database is needed. To provide it, we can use one of query execution methods:

    let blog = getBlog id |> run

for synchronous execution, or

    async {
        let! blog = getBlog id |> runAsync
        ...
    }

for asynchronous one.

When more than one query should be executed in context of one open connection, the function with DataContext parameter can be defined:

    let insertPostWithTags (p: Post) (ctx: DataContext) = 
        let postId = insertPost p ctx
        insertTags postId p.tags ctx

    insertPostWithTags p |> run

But there is even better approach. Functions of type DataContext -> 't are examples of Reader monad and it’s possible to create computation expression for them. SqlFun provides one:

    dbaction {
        let! postId = insertPost p
        do! insertTags postId p.tags 
    } |> run

There is also asynchronous version:

    asyncdb {
        let! postId = insertPost p
        do! insertTags postId p.tags
    } |> runAsync |> Async.Start

Of course, nothing prevents you from creating connection manually, and executing query within a use block, but I strongly believe, that it’s not a proper way of doing things in functional language.