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How to alter table in SQL Server?

To alter an existing table in SQL Server, you can use SQL Server Management Studio (SSMS) or execute SQL commands using a query window. Here's a step-by-step guide on how to alter a table:

Using SQL Server Management Studio (SSMS):

  1. Open SSMS and connect to your SQL Server instance.
  2. In the Object Explorer pane, expand the database containing the table you want to alter.
  3. Expand the "Tables" folder and locate the specific table you want to alter.
  4. Right-click on the table and select "Design" to open the table designer.
  5. In the table designer, you can make various modifications to the table structure, such as adding, modifying, or dropping columns, changing data types, setting constraints, and more.
  6. To add a new column, right-click on the table design grid and select "Add Column." Specify the column name, data type, and any additional properties.
  7. To modify an existing column, locate the column in the table designer, and make the necessary changes to the column name, data type, or other properties.
  8. To drop a column, right-click on the column and select "Delete."
  9. Once you have made the desired alterations, click the "Save" button or press Ctrl+S to save the changes to the table.

Using SQL Commands:

  1. Open SSMS and connect to your SQL Server instance.
  2. Open a new query window by clicking "New Query" in the toolbar or pressing Ctrl+N.
  3. Execute the ALTER TABLE statement to modify the table structure.
    For example, to add a new column:
    
ALTER TABLE TableName
ADD NewColumn INT;
    Replace "TableName" with the name of the table you want to alter and specify the new column name and data type.
  4. To modify an existing column:
    
ALTER TABLE TableName
ALTER COLUMN ExistingColumn VARCHAR(100);
    Replace "TableName" with the name of the table and specify the existing column name and the new data type.
  5. To drop a column:
    
ALTER TABLE TableName
DROP COLUMN ColumnName;
    Replace "TableName" with the name of the table and specify the column name to be dropped.
  6. Execute the query by clicking the "Execute" button or pressing F5 to apply the alterations to the table.

    7. Please note that altering a table may impact the existing data and queries relying on the table structure. Take necessary precautions and backup your data before making any modifications to a table.

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