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How will you create a table with composite primary key in SQL Server?

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How will you create a table with composite primary key in SQL Server?

Composite key is a key which is the combination of more than one field or column of a given table. It may be a candidate key or primary key. Columns that make up the composite key can be of different data types….

  1. CREATE TABLE SAMPLE_TABLE.
  2. (COL1 integer,
  3. COL2 varchar(30),
  4. COL3 varchar(50),
  5. PRIMARY KEY (COL1, COL2));

How will you create a table with composite primary key in MySQL?

You can create a MySQL composite Primary Key in the following two ways:

  1. During table creation using CREATE TABLE statement.
  2. After creating tables using ALTER TABLE statement.

Can we create composite key with primary key?

When over one column or field in a table are combined to achieve the task of uniquely identifying row values, then that composite key can be either a primary or a candidate key of that table.

How do I add a composite key to a table?

Now, execute the ALTER TABLE statement to add a composite primary key as follows: ALTER TABLE Student add primary key(stud_id, subject);…Composite Key Using ALTER TABLE Statement

  1. CREATE TABLE Student(
  2. stud_id int NOT NULL,
  3. stud_code varchar(15),
  4. stud_name varchar(35),
  5. subject varchar(25),
  6. marks int.
  7. );

What is composite key give an example?

In a table representing students our primary key would now be firstName + lastName. Because students can have the same firstNames or the same lastNames these attributes are not simple keys. The primary key firstName + lastName for students is a composite key.

How do you write a composite attribute in SQL?

No, MySQL doesn’t support “composite” attributes. You could “break out” the components of the “composite” attribute into a separate table. Or, you can keep them as individual columns in the same table. I use the column name to “identify” the attributes that make up a composite attribute.

How do you create an index on a composite primary key?

You can create an index for composite primary key that uses the same fields present in your composite primary key. mysql> alter table new_orders ADD INDEX new_index (order_id, product_id); Hopefully, now you can create composite primary key in MySQL.

What is composite key in SQL with example?

A composite key specifies multiple columns for a primary-key or foreign-key constraint. The next example creates two tables. The first table has a composite key that acts as a primary key, and the second table has a composite key that acts as a foreign key.

How do I create a composite attribute in SQL?

Can a table have both primary key and composite key?

A table can have only one primary key, which may consist of single or multiple fields. When multiple fields are used as a primary key, they are called a composite key. If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).

How do you use a composite primary key in a select statement?

This can be done by the “ALTER” command.

  1. ALTER Composite Key. If you want to alter the composite key from the existing table. We use the below syntax. Syntax: Alter table
  2. DROP Composite Key. If you want to drop the composite key from the existing table. We use the below syntax. Syntax: Alter table

What is a composite key with example?