SQL SELECT hierarchy

1. How do I SELECT a hierarchy in SQL?
2. How do I SELECT top 5 records in SQL?
3. What is the order of SQL query execution?
4. What is hierarchical data in SQL?

How do I SELECT a hierarchy in SQL?

Use hierarchyid as a data type to create tables with a hierarchical structure, or to describe the hierarchical structure of data that is stored in another location. Use the hierarchyid functions in Transact-SQL to query and manage hierarchical data.

How do I SELECT top 5 records in SQL?

Example - Using TOP keyword

For example: SELECT TOP(5) contact_id, last_name, first_name FROM contacts WHERE last_name = 'Anderson' ORDER BY contact_id; This SQL SELECT TOP example would select the first 5 records from the contacts table where the last_name is 'Anderson'.

What is the order of SQL query execution?

SQL queries adhere to a specific order when evaluating clauses, similar to how mathematical operations adhere to PEMDAS or BIDMAS. From the eyes of the user, queries begin from the first clause and end at the last clause. However, queries aren't actually read from top to bottom when carried out.

What is hierarchical data in SQL?

Hierarchical data is defined as a set of data items that are related to each other by hierarchical relationships. Hierarchical relationships exist where one item of data is the parent of another item.