How can the column names and constraints of a SQL Server Table be altered?

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To alter the column names and constraints of a SQL Server table, the following steps can be followed:

1. To alter the column name:

   ALTER TABLE tablename RENAME COLUMN oldcolumnname TO newcolumn_name;

   For example:

   ALTER TABLE customers RENAME COLUMN custname TO customer_name;

2. To add a constraint:

   ALTER TABLE tablename ADD CONSTRAINT constraintname constrainttype (columnname);

   For example:

   ALTER TABLE orders ADD CONSTRAINT fkcustomerid FOREIGN KEY (customerid) REFERENCES customers (customer_id);

3. To drop a constraint:

   ALTER TABLE tablename DROP CONSTRAINT constraintname;

   For example:

   ALTER TABLE orders DROP CONSTRAINT fk_customerid;

Note: Make sure to replace "tablename", "oldcolumnname", "newcolumnname", "constraintname", "constrainttype" and "columnname" with the actual names of the table, column, and constraint.