What is PL/SQL?

To delete a table in SQL Server, you can use the DROP TABLE statement. Make sure you have the necessary permissions to perform this action, as it will permanently remove the table and its data from the database. Here's the basic syntax:

DROP TABLE [schema_name.]table_name;

Replace schema_name with the name of the schema where the table resides (if applicable), and replace table_name with the name of the table you want to delete.

For example, to delete a table named "Employees" from the "dbo" schema:

DROP TABLE dbo.Employees;

If the table has any associated constraints, triggers, or indexes, you may need to drop those objects first before you can successfully delete the table. Be cautious when using this command, as data loss is irreversible.

Remember to take a backup of your database before performing any critical operations like dropping a table, especially in a production environment.

To update an existing Table we use SQL Command UPDATE: It will update the records as per user defined query/need.

Update TableName SET ColumnName = NewData where Condition   
Update info Set City = 'Baroda' where id = 2  

Relationships are created by linking the column in one table with the column in another table. There are four different types of relationship that can be created.

The relationships are listed below:

1. One to One Relationship
2. Many to One relationship
3. Many to Many relationship
4. One to One relationship

Answer 1:

A table column with this constraint is called the key column for the table. This constraint helps the table to make sure that the value is not repeated and also that there are no null entries. This column does not allow null values and duplicate values. You can try inserting values to violate these conditions and see what happens. A table can have only one Primary key. Multiple columns can participate on the primary key.

Answer 2:

A primary key is a combination of fields which uniquely specify a row. This is a special kind of unique key, and it has implicit NOT NULL constraint. It means, Primary key values cannot be NULL.

CREATE TABLE Customers (
    CustomerID INT PRIMARY KEY,
    FirstName VARCHAR(50),
    LastName VARCHAR(50),
    Email VARCHAR(100)
);