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.

Filtering with WHERE

Column does not exist

Functions in WHERE

Test your knowledge of WHERE

Filtering with HAVING

Row filtering with HAVING

Filtering with WHERE and HAVING

Test your knowledge of HAVING

Interrogation after SELECT

SELECT what you need

Limit the rows with TOP

Should I use ORDER BY?

Managing duplicates

Remove duplicates with DISTINCT()

UNION and UNION ALL

UNION or 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.

Zeitstatistiken

STATISTICS TIME in Abfragen

STATISTICS TIME-Ergebnisse

Statistiken zu Page Reads

STATISTICS IO: Beispiel 1

STATISTICS IO: Beispiel 2

STATISTICS IO: Vergleich

Indizes

Teste dein Wissen über Indizes

Clustered Index

Ausführungspläne

Sort-Operator in Ausführungsplänen

Teste dein Wissen über Ausführungspläne

Query Performance Tuning: Schlussbemerkungen

Query performance tuning

Orders dataset

NBAPlayers dataset

NBATeams dataset

NBAPlayersStatistics dataset

Ein geschäftskritischer Auftrag hängt von deinen SQL-Kenntnissen ab. Du hast Code bekommen, den du reparieren sollst. Er liefert zwar die gewünschten Ergebnisse, läuft aber zu langsam und ist schlecht formatiert, was das Lesen erschwert. Die Deadline ist morgen. Du musst den Code neu formatieren und verschiedene Methoden ausprobieren, um die Leistung zu verbessern. Der Druck ist hoch!!! In diesem Kurs arbeiten wir mit SQL an realen Datensätzen – von Sport bis Geowissenschaft – und schauen uns gute Coding-Praktiken sowie verschiedene Wege an, wie wir die Performance von Abfragen verbessern können, um das gleiche Ergebnis zu erreichen.

Intermediate SQL Server

Entdecken Sie, wie Sie Code umformatieren und Methoden testen, um SQL-Abfragen zu optimieren.

Verbesserung der Abfrageleistung in SQL Server

In diesem Kurs lernst du, effiziente Abfragen zu schreiben, die leicht lesbar und verständlich sind.

SQL Server-Entwickler

SQL Server für Datenbankadministratoren

Teste dein Wissen über Indizes

Interaktive praktische Übung