In this chapter, students will learn how SQL code formatting, commenting, and aliasing is used to make queries easy to read and understand.  Students will also be introduced to query processing order in the database versus the order of the SQL syntax in a query.

Introduction

Formatting - player BMI

Commenting - player BMI

Commenting - how many Kiwis in the NBA?

Aliasing

Ambiguous column names

Aliasing - team BMI

Query order

Processing order

Syntax order - New Zealand earthquakes

Syntax order - Japan earthquakes

Syntax order - very large earthquakes

 Introduction, Review and The Order of Things

This chapter introduces filtering with WHERE and HAVING and some best practices for how (and how not) to use these keywords. Next, it explains the methods used to interrogate data and the effects these may have on performance.  Finally, the chapter goes over the roles of DISTINCT() and UNION in removing duplicates and their potential effects on performance.

Filteren met WHERE

Kolom bestaat niet

Functies in WHERE

Test je kennis van WHERE

Filteren met HAVING

Rijfiltering met HAVING

Filteren met WHERE en HAVING

Test je kennis van HAVING

Onderzoeken na SELECT

SELECT wat je nodig hebt

Beperk het aantal rijen met TOP

Moet ik ORDER BY gebruiken?

Duplicaten beheren

Dubbele waarden verwijderen met DISTINCT()

UNION en UNION ALL

UNION of DISTINCT()?

Filtering and Data Interrogation

This chapter is an introduction to sub-queries and their potential impacts on query performance.  It also examines the different methods used to determine if the data in one table is present, or absent, in a related table.

Sub-queries

Uncorrelated sub-query

Correlated sub-query

Sub-query vs INNER JOIN

Presence and absence

INTERSECT

EXCEPT

Interrogating with INTERSECT

Alternative methods 1

IN and EXISTS

NOT IN and NOT EXISTS

NOT IN with IS NOT NULL

Alternative methods 2

INNER JOIN

Exclusive LEFT OUTER JOIN

Test your knowledge

Sub-queries and presence or absence

Students are introduced to how STATISTICS TIME, STATISTICS IO, indexes, and executions plans can be used in SQL Server to help analyze and tune query performance.

Time statistics

STATISTICS TIME in queries

STATISTICS TIME results

Page read statistics

STATISTICS IO: Example 1

STATISTICS IO: Example 2

STATISTICS IO comparison

Indexes

Test your knowledge of indexes

Clustered index

Execution plans

Sort operator in execution plans

Test your knowledge of execution plans

Query performance tuning: final notes

Query performance tuning

Orders dataset

NBAPlayers dataset

NBATeams dataset

NBAPlayersStatistics dataset

Een bedrijfskritische opdracht hangt af van je SQL-vaardigheden. Je hebt code gekregen om te repareren. De code levert wel de juiste resultaten op, maar draait te langzaam en is slecht opgemaakt, waardoor hij lastig te lezen is. De deadline is morgen. Je moet de code opnieuw opmaken en verschillende methoden proberen om de prestaties te verbeteren. De druk staat erop!!! In deze cursus gebruiken we SQL op datasets uit de echte wereld, van sport tot geowetenschap, om te kijken naar goede codeerpraktijken en verschillende manieren waarop we de prestaties van queries kunnen verbeteren om hetzelfde resultaat te bereiken.

Intermediate SQL Server

Ontdek hoe je code kunt herformatteren en methoden kunt proberen om SQL-queryprestaties te verbeteren.

De queryprestaties verbeteren in SQL Server

In deze cursus leren studenten om query's te schrijven die zowel efficiënt als makkelijk te lezen en te begrijpen zijn.

SQL Server-ontwikkelaar

SQL Server voor databasebeheerders

Test je kennis van WHERE

De queryprestaties verbeteren in SQL Server

Praktische interactieve oefening