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A Subquery/ Inner query/ Nested query is a query within another SQL outer query and embedded within the WHERE clause. A subquery (also known as a nested query or inner query) in SQL is a query nested inside another query. It is used to retrieve data …

An Auto Increment/Identity column in SQL Server is a column that automatically generates a unique value for each new row inserted into a table. It is often used as a primary key to ensure each record has a distinct identifier. The column's valu…

A join clause is used to combine rows from two or more tables, based on a related column between them. Joins in SQL are used to combine data from two or more tables based on a related column. They enable retrieval of data from multiple tables in a si…

There are four types of joins in SQL Server: Left outer join - A left join returns all the rows from the left table, along with any matching rows from the right table.  Right outer join - A right join returns all the rows from the right table, alon…

A self-join is a type of SQL join where a table is joined with itself. It is used to combine rows from the same table based on a related column, typically with different aliases for the table to distinguish between the two instances. Self-joins are us…

Indexes in SQL Server are database objects that improve the performance of queries by providing a quick and efficient way to access data. They act like a roadmap, allowing the database engine to locate specific rows faster, especially when searching f…

A clustered index is a type of index that determines the physical order of data in a table. Table data can be sorted in only way, therefore, there can be only one clustered index per table. In SQL Server, if you set a primary key on a column, then it …

A non-clustered index is stored at one place and table data is stored in another place. A table can have multiple non-clustered index in a table. A non-clustered index in SQL Server is a database index that improves query performance for specific col…

A clustered index is a type of index that determines the physical order of data in a table. A non-clustered index is stored at one place and table data is stored in another place. For example, Book Index. A table can have only one clustered index. A t…

In SQL Server, you can create both clustered and non-clustered indexes using the CREATE INDEX statement. The syntax for creating clustered and non-clustered indexes is slightly different. Below are examples of how to create both types of indexes in …

To optimize the given query "select id, class from student where name='happy'", you should apply indexing on the "name" column in the "student" table. Indexing the "name" column will help speed up the se…