SQL 101 - SELECT

The first thing you need to know when learning SQL is how to get data out of a database.  This means learning the SELECT command.  Using this command will get the SQL server to return data to you. You can use this command to do some simple math, or to do the common "Hello World!" application you all learn the first day of a programming course.

SELECT 1 + 1

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output
 2

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SELECT 'Hello World'

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output
Hello World

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Keeping this in mind can become useful later, when you need to have the server return debugging statements to you during particularly long code writing sessions.  But usually you'll need the SELECT command to lookup a certain piece of data from a table.  Let's assume you have a table of products.  In this table there are several columns, one of which is productName.  If you wanted to get a list of every product in your table, you can write the following command:

SELECT
   productName
FROM products

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output

  productName
  -----------
  pencil
  pen
  paper
  Mountain Dew

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I'd like to point out the data returned is not ordered.  In later articles I'll show you how to put the results into any order you may find useful.  But for now, let's stick to learning about the SELECT statement.

What if you wanted to know the name and the price?  In SQL you can list as many columns as you like, in a comma separated list.

SELECT
   productName, price
FROM products

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output

  productName     price
  -----------     -----
  pencil          .25
  pen             .99
  paper          1.00
  Mountain Dew   1.25

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Finally, if you want to return all the data of the table, you can do that too.  But I would like to point out using the following command on a table a lot of rows (thousands, or millions) could be very time and processor consuming.  Use this only if you know the number of records and columns will be small enough your server and connection can handle.  There are also many reasons NOT to use this, but I'll show you how to do it anyway.

SELECT  *
FROM products

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output

  productName     price   quantity   color
  -----------     -----   --------   -----
  pencil          .25      100        yellow
  pen             .99       73        blue
  paper          1.00      500        white
  Mountain Dew   1.25        8        green

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As always, if you have any questions, please let me know!  I'm here to help you understand SQL Server better.  Let me know how I can do that.