SQL

What is SQL?

SQL stands for Structured Query Language. It is used to define data structures, query data and apply changes. A SELECT, for example, selects data. SQL is not a single database product; systems implement it with different extensions and details. A query cannot therefore be assumed transferable to every system without checking.

In a fictional service portal, a list of approved requests should be sorted by their unique identifier. An example read query is: SELECT request_id FROM service_request WHERE status = 'approved' ORDER BY request_id;. It explicitly names the output column, a condition and the sorting. This is not an executed query. The solution must separately enforce which records a person may see; a business filter condition alone does not demonstrate access control.

Sources

• PostgreSQL · The SQL Language

• PostgreSQL · Introduction

• PostgreSQL · Querying a Table