![]() ![]() default_value: specify the value that you want to insert – an integer, character, or character string.column_name: specify the name of the column where you want to create the default constraint. ![]() constraint_name: specify the desired constraint name.tbl_name: specify the name of the table where you want to add the default constraint.To add a constraint on an existing column of the table, we use the ALTER TABLE ADD CONSTRAINT statement: ALTER TABLE ĪDD CONSTRAINT DEFAULT FOR Adding a DEFAULT Constraint Into Existing Table SQL Server has created a constraint with the system-generated name. Run the following script to view the constraint name: SELECT NAME , SQL Server creates a constraint with a system-generated unique name.Ĭreate the table using the below query: USE demodatabase While creating a table, we do not specify the name of the DEFAULT constraint. Use the following query to view data from the table: INSERT INTO salesdetailsĪs you can see, the zero has been inserted into the Sale_Qty column. Execute the following query: INSERT INTO salesdetails Now, let us test the constraint behavior by inserting some dummy records into it. Sale_qty INT CONSTRAINT df_salesdetails_saleqty DEFAULT 0 To do that, I am creating a default constraint named DF_SalesDetails_SaleQty on the Sale_Qty column. When we insert data into the table without specifying the Sale_Qty column value, the query must insert zero. ![]() Adding a DEFAULT Constraint While Creating a New Table To create a default constraint, you need the ALTER TABLE and CREATE TABLE permission. When we execute the INSERT statement but do not specify any value for the column with the default constraint created, SQL Server inserts the default value specified in the DEFAULT constraint definition. What is DEFAULT CONSTRAINT in SQL Server?Ī default constraint specifies the default value for the column.
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