How to Alter Default Value of Column in SQL Server
In SQL Server, altering the default value of a column is a common task that can be performed using the ALTER TABLE statement. The default value is a constant value that is automatically inserted into a column if no other value is specified during an INSERT operation. This article will guide you through the steps to alter the default value of a column in SQL Server.
Firstly, it is important to identify the table and column for which you want to change the default value. Once you have this information, you can proceed with the following steps:
1. Open SQL Server Management Studio (SSMS) and connect to your database server.
2. In the Object Explorer, expand the server tree, then expand the database where your table is located.
3. Right-click on the table and select “ALTER TABLE” to open the table designer.
4. In the table designer, locate the column for which you want to change the default value.
5. In the “Default Value” column, you will see the current default value. Replace it with the new default value you want to set.
6. Click “Save” to apply the changes.
If you prefer to use Transact-SQL (T-SQL) commands, you can execute the following script to alter the default value of a column:
“`sql
ALTER TABLE table_name
ALTER COLUMN column_name column_data_type DEFAULT new_default_value;
“`
Replace `table_name` with the name of your table, `column_name` with the name of the column, `column_data_type` with the data type of the column, and `new_default_value` with the new default value you want to set.
Before making any changes, it is crucial to ensure that the new default value is appropriate for the column’s data type. For example, if the column is of type `INT`, the default value should be a numeric value. Additionally, consider the following points when altering the default value of a column:
– The new default value must be compatible with the column’s data type.
– The default value should be a constant value; you cannot set a default value that depends on other columns or tables.
– If the table contains existing rows, changing the default value will not affect those rows. The new default value will only apply to new rows inserted after the change.
In conclusion, altering the default value of a column in SQL Server is a straightforward process that can be done using either the table designer in SSMS or T-SQL commands. Always ensure that the new default value is appropriate for the column’s data type and consider the implications of the change on existing and new rows in the table.
