SQL PROGRAMMING FOR BEGINNERS: THE GUIDE with STEP BY STEP processes on DATA ANALYSIS, DATA ANALITICS and PROGRAMMING LANGUAGE. learn sql server technique for analyzing and manipulating the codes by Machina Richard

Author:Machina, Richard [Machina, Richard]
Language: eng
Format: azw3
Published: 2020-05-17T16:00:00+00:00

Chapter 6 Data Query Language (Dql)

A query, is, simply put, a set of instructions you give in order to change a table within a database. The ones we will be looking at are primarily the UPDATE and DELETE queries.

Both of these queries are very self-explanatory. The UPDATE query will take the information currently within a table, and change it to whatever you desire. The DELETE query is quite like an UPDATE query just with “null” instead of what you wanted to change it to. It will delete any entries that you wish.

It is important to note that while these queries are extremely important, they’re also inefficient. You’ll learn that there are much more efficient ways to do what these queries do, and at a much larger scale.

With that being said, they are still a must-learn for budding developers. They help you learn the fundamental blocks that advanced SQL is based on. After all, every business owner has heard horror stories of developers that only know higher-level material, and low-level techniques become their downfall.

These queries will primarily be useful in debugging and lower-level positions. Otherwise, they’re only useful for manually editing smaller tables, at which point you might as well use Excel instead of SQL.

On the other side of the coin, we have the TOP query. The TOP query, rather than actually changing the information inside a table, shows you only specific entries from a table. To be precise, the TOP query will show you the topmost N or topmost N % of a given table.

This is especially useful if you’re using SQL for math or science, in which case it can make recurring certain functions very easy.

The LIKE clause is meant to compare different objects/strings while the ORDER BY clause will sort a table in ascending or descending order, as you feel fit.

These are two extremely powerful tools that you'll use throughout your career as a SQL developer, so let’s dive right in!

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