Tables that define the primary key as a clustered index:Īs you can see, the first table which uses NEWID() generates random values while The IDENTITY property takesĪn initial seed value as its first parameter and an increment value as its secondĬonsider the following example which creates and inserts into identity based The way the property has been declared on the column. Once defined, the engine will automatically generate a sequential number based on The IDENTITY column property on a column that's typically declared as an integer. The most common, well known way to auto-generate a key value is via the use of Replication to uniquely identify rows in Merge Replication or Transactional Replication Furthermore, GUIDs are heavily used in SQL Server The most common ways are via the use of the IDENTITY column property or by specifyingĪ uniqueidentifier (GUID) data type along with defaulting with either the NEWID() Either way, both are generated by NEWID() so we effectively get the same result – a randomly generated GUID.Yes, there are a number of ways you can auto-generate key values for your tables. Here I use NEWID() to generate a unique ID for each row, and therefore the default value isn’t used. ![]() INSERT Customer (CustomerId, CustomerName) You can also explicitly use NEWID() when inserting the data. Example 5 – Explicitly Specified in the INSERT Statement Finally, I select the contents of the table, which shows use the GUID that was generated with each row insert. When I do this, I don’t specify the CustomerId value, so it uses the default value (which is generated by NEWID()). In this example, I create a table that includes a uniqueidentifier column with its default value generated by NEWID(). Here’s an example of using NEWID() as a default value in a database column.ĬustomerId uniqueidentifier NOT NULL DEFAULT NEWID(), Here’s an example of converting the variable value to a string, then printing it out. Here’s an example of putting the value of NEWID() into a variable, then selecting it. Example 2 – Using NEWID() with a Variable When you look at all the examples on this page, you’ll notice that they’re all unique, but they all take the form: xxxxxxxx-xxxx-4xxx-xxxx-xxxxxxxxxxxx, which means they’re all version 4 GUIDs, and therefore they’re all randomly or pseudo-randomly generated. Other versions use other methods to generate the GUID. ![]() Version 4 specifies that the GUID is randomly or pseudo-randomly generated. I can tell that this example uses RFC4122 version 4, because of the 4 in the relevant spot. RFC4122 includes 5 versions (or sub-types). Here’s a quick SELECT statement that returns NEWID(): This is also known as a UUID (Universally Unique IDentifier). ![]() The value that NEWID() produces is a randomly generated 16-byte GUID (Globally Unique IDentifier). More specifically, it’s an RFC4122-compliant function that creates a unique value of type uniqueidentifier. In SQL Server, you can use the NEWID() function to create a unique value.
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