![]() ![]() A CREATE VIEW statement produces an error if a table with the same name already exists in the. With this new knowledge at our fingertips, we can rewrite our previous CREATE TABLE statement by adding our two new constraints. When we create the tables to store the data in the database, at that time to recognize the row and identify each of the records stored in the table, we use. A schema cannot contain a table and view with the same name. While IDENTITY can accept two arguments of the numeric seed where the values will begin from as well as the increment, these values are typically not specified with the IDENTITY constraint and instead are left as defaults (both default to 1). The second piece of the puzzle is the IDENTITY constraint, which informs SQL Server to auto increment the numeric value within the specified column anytime a new record is INSERTED. In a multi-column scenario, individual columns can contain duplicate, non-unique values, but the PRIMARY KEY constraint ensures that every combination of constrained values will in fact be unique relative to every other combination. A VIEW is a stored query - you cant have KEYs on a query. While SQL Server only allows one PRIMARY KEY constraint assigned to a single table, that PRIMARY KEY can be defined for more than one column. You have to put PRIMARY KEYs and INDEXes on the underlying tables. The first is PRIMARY KEY, which as the name suggests, forces the specified column to behave as a completely unique index for the table, allowing for rapid searching and queries. The solution turns out to be using two constraint options provided by SQL Server. ![]() Using Identity and Primary Key Constraints When a new record is inserted, we not only must manually enter a value for id, but we have to perform a query ahead of time to attempt to verify that id value doesn’t already exist (a near-impossibility when dealing with many simultaneous connections). ![]() The problem here is, we have no way of controlling our id field. CREATE TABLE books ( id INT NOT NULL, title VARCHAR ( 100 ) NOT NULL, primary_author VARCHAR ( 100 ), ) ![]()
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