How to get latest date from a column in a table in sql?

Question

I'm trying to get the latest date from my OrderItem table using sql, asp.net. However, when i run the program, they show this error: Incorrect syntax near the keyword 'from'.

Here are my codes:

    string strconnect =  ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
    SqlConnection myConnect = new SqlConnection(strconnect);

    string command = "
      Select OrderItem.ProductID, Product.Name, OrderItem.TotalQty, Product.UnitPrice, OrderItem.TotalPrice 
      FROM OrderItem 
      INNER JOIN Product ON OrderItem.ProductID=Product.ProductID 
      WHERE OrderDate = MAX(OrderDate) from OrderItem";
    SqlCommand cmd = new SqlCommand(command, myConnect);

    myConnect.Open();

    SqlDataReader reader = cmd.ExecuteReader();

    GridView1.DataSource = reader;
    GridView1.DataBind();
    reader.Close();
    myConnect.Close();

Please advise!

Answer 1

You need to remove "from OrderItem" in your WHERE condition since you have specified in your FROM clause.

SELECT
    i.ProductID,
    p.Name,
    i.TotalQty,
    p.UnitPrice,
    i.TotalPrice 
FROM 
    OrderItem i
        INNER JOIN Product p
            ON i.ProductID = p.ProductID 
WHERE
    i.OrderDate = (SELECT MAX(OrderDate) 
                   FROM OrderItem 
                   WHERE OrderItem.ProductID = i.ProductID)

Answer 2

SELECT o.ProductID, p.Name, o.TotalQty, p.UnitPrice, o.TotalPrice 
FROM OrderItem AS o
INNER JOIN Product AS p ON o.ProductID = p.ProductID
ORDER BY o.OrderDate DESC
LIMIT 1

Ahh, you are using SQL-server, try this: (however not tested)

SELECT TOP 1 o.ProductID, p.Name, o.TotalQty, p.UnitPrice, o.TotalPrice 
FROM OrderItem AS o
INNER JOIN Product AS p ON o.ProductID = p.ProductID
ORDER BY o.OrderDate DESC

Answer 3

It depends on what is data type of order date. You may need to change the data type of the variable or apply truncation.

declare @MaxOrderDate datetime
select @MaxOrderDate = MAX(OrderItem.OrderDate) from OrderItem

Select
    OrderItem.ProductID,
    Product.Name,
    OrderItem.TotalQty,
    Product.UnitPrice,
    OrderItem.TotalPrice 
FROM 
    OrderItem 
        INNER JOIN Product 
            ON OrderItem.ProductID=Product.ProductID 
WHERE
    OrderItem.OrderDate = @MaxOrderDate

Answer 4

You should change the subquery in the WHERE clause.

SELECT OrderItem.ProductID, Product.Name, OrderItem.TotalQty, Product.UnitPrice, OrderItem.TotalPrice 
FROM OrderItem 
INNER JOIN Product ON OrderItem.ProductID=Product.ProductID 
WHERE OrderDate = ( SELECT MAX(OrderDate) FROM OrderItem );