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daily 08/04/2015

    • In a statement to the Dallas Morning News, Fox Sports denied that James was fired for his religious beliefs, but rather because he “abused a previous on-air position to further a personal agenda,” presumably referring to the fact that James began running for office while still an ESPN employee. Here’s the statement:
    • “All I remember is that I couldn’t breathe,” says Ryan. “I thought I was going to black out and die, when all of a sudden I see two big arms tossing bodies off of me. It was [Chicago’s] Bo Jackson. He had come to my rescue, and I’m awful glad he did, because I was about to pass out. I called him that night and thanked him.”
    • Many tables, including fact tables, have primary keys. For most tables, such as those that contain customer, employee, or sales data, you’ll want the table’s primary key so that you can use it to create relationships in the model.
    • Fact tables are different. In a fact table, the primary key is used to uniquely identify each row. While necessary for normalization purposes, it’s less useful in a data model where you want only those columns used for analysis or to establish table relationships. For this reason, when importing from a fact table, do not include its primary key. Primary keys in a fact table consume enormous amounts of space in the model, yet provide no benefit, as they cannot be used to create relationships.
    •    In data warehouses and multidimensional databases, large tables consisting of mostly numeric data are often referred to as “fact tables”. Fact tables typically include business performance or transaction data, such as sales and cost data points that are aggregated and aligned to organizational units, products, market segments, geographical regions, and so on.
      • Datetime columns include a date part and a time. When you ask yourself whether you need a column, ask the same question multiple times for a Datetime column:




          Do I need the time part?




          Do I need the time part at the level of hours? , minutes? , Seconds? , milliseconds?




          Do I have multiple Datetime columns because I want to calculate the difference between them, or just to aggregate the data by year, month, quarter, and so on.

    • To make query modification easier, you should filter out at least one column in every table. By filtering out a column, you change query construction from an abbreviated format (SELECT *) to a SELECT statement that includes fully-qualified column names, which are far easier to modify.
    • If you need hours and minutes, and you prefer them together as one time column, you can use the syntax :


      Timefromparts(datepart(hh, dbo.Bigtable.[Date Time]), datepart(mm, dbo.Bigtable.[Date Time])) as [Date Time HourMinute]

    • One memory-saving technique is to replace regular or calculated columns with calculated measures. The classic example is Unit Price, Quantity, and Total. If you have all three, you can save space by maintaining just two and calculating the third one using DAX.

Posted from Diigo. The rest of my favorite links are here.

Categories: Uncategorized
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