# SQL Questions

Q:

Mention the difference between clustered and a non-clustered index?

- A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index.

- A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

Subject: SQL - Technology

1977
Q:

What UNION does in SQL?

In SQL, UNION  merges the contents of two structurally-compatible tables into a single combined table.