Beginning SQL queries: from novice to professional [Second edition] 9781484219546, 9781484219553, 1484219546, 1484219554

Table of contents :
Contents at a Glance......Page 6
Contents......Page 8
About the Author......Page 16
About the Technical Reviewer......Page 18
Acknowledgments......Page 20
Introduction......Page 22
Introducing Database Tables......Page 24
Attributes......Page 25
Inserting and Updating Rows in a Table......Page 26
Designing Appropriate Tables......Page 28
Introducing Data Models......Page 29
Retrieving Information from a Database......Page 32
Process Approach......Page 33
Outcome Approach......Page 34
Why We Consider Two Approaches......Page 35
Summary......Page 36
Subsets of Rows and Columns......Page 37
Using Aliases......Page 40
Comparison Operators......Page 41
Logical Operators......Page 43
Dealing with Nulls......Page 45
Comparisons Involving Null Values......Page 46
Managing Duplicates......Page 47
Ordering Output......Page 50
Avoiding Common Mistakes......Page 51
Incorrectly Using a WHERE Clause to Answer Questions with the Word “both”......Page 52
Summary......Page 54
Cartesian Product......Page 55
Inner Join......Page 57
Outcome Approach to Joins......Page 58
Extending Join Queries......Page 60
A Process Approach......Page 61
Order of Operations......Page 63
An Outcome Approach......Page 64
Expressing Joins Through Diagrammatic Interfaces......Page 65
Other Types of Joins......Page 66
Outer Joins......Page 67
Summary......Page 70
IN Keyword......Page 72
Using IN with Subqueries......Page 73
Being Careful with NOT and ......Page 75
EXISTS Keyword......Page 78
Inner Queries Returning a Single Value......Page 81
Inner Queries Checking for Existence......Page 83
Using Subqueries for Updating......Page 84
Summary......Page 85
A subquery checking for existence......Page 86
Update data......Page 87
Self Relationships......Page 88
Creating a Self Join......Page 91
What Are the Names of the Coaches?......Page 92
List the Names of All Members and the Names of Their Coaches......Page 93
Who Coaches the Coaches, or Who Is My Grandmother?......Page 95
An Outcome Approach to Self Joins......Page 97
Questions Involving “Both”......Page 100
An Outcome Approach to Questions Involving “Both”......Page 101
A Process Approach to Questions Involving “Both”......Page 102
Questions Involving the Word “Both”......Page 103
Two Relationships Between the Same Tables......Page 105
Extracting Information from Multiple Relationships......Page 109
Process Approach......Page 110
Outcome Approach......Page 113
Business Rules......Page 114
Summary......Page 117
Overview of Basic Set Operations......Page 118
Union-Compatible Tables......Page 120
Ensuring Union Compatibility......Page 123
Union......Page 124
Selecting the Appropriate Columns......Page 125
Uses of Union......Page 127
Union and Full Outer Joins......Page 128
Intersection......Page 130
Uses of Intersection......Page 131
The Importance of Projecting Appropriate Columns......Page 134
Managing Without the INTERSECT Keyword......Page 135
Uses of Difference......Page 137
Managing Without the EXCEPT Keyword......Page 140
Division......Page 141
Projecting Appropriate Columns......Page 143
SQL for Division......Page 144
Summary......Page 145
Difference......Page 146
Division......Page 147
The COUNT() Function......Page 148
Managing Nulls......Page 149
The AVG() Function......Page 151
Managing Duplicates......Page 152
The ROUND() Function......Page 153
Grouping......Page 154
Filtering the Result of an Aggregate Query......Page 159
Using Aggregates to Perform Division Operations......Page 161
Nested Queries and Aggregates......Page 163
Summary......Page 165
Simple Aggregates......Page 166
Partitions......Page 168
Cumulative Aggregates......Page 169
Ranking......Page 171
Combining Ordering with Partitions......Page 172
Framing......Page 175
OVER(ROWS BETWEEN AND )......Page 178
What Happens to a Query......Page 179
Storing Records in Order......Page 181
Clustered Index......Page 182
Non-Clustered Indexes......Page 183
Clustered Index on a Compound Key......Page 184
Updating Indexes......Page 185
Join Techniques......Page 186
Nested Loops......Page 187
Merge Join......Page 188
Different SQL Expressions for Joins......Page 189
Use the Tools......Page 191
Determine the Relationships Between Tables......Page 192
Real World Versus Implementation......Page 195
Look at Some Data Values......Page 197
Combine the Tables......Page 198
Retain the Appropriate Columns......Page 200
Spotting Keywords in Questions......Page 201
And, Both, Also......Page 202
Not, Never......Page 204
All, Every......Page 205
Try to Answer the Question by Hand......Page 206
Are There Alternatives?......Page 207
Checking Queries......Page 208
Check Boundary Conditions......Page 209
Summary......Page 210
Data That Is Not Normalized......Page 212
Tables with No Primary Key......Page 215
Similar Data in Two Tables......Page 216
Inappropriate Types......Page 217
Unexpected Nulls......Page 218
Extraneous Characters in Text Fields......Page 219
Diagnosing Problems......Page 220
Retain All the Columns......Page 221
Should You Have an Outer Join?......Page 222
Have You Used AND Instead of OR?......Page 223
Did You Use NOT Instead of Difference?......Page 224
Incorrect Statistics or Aggregates......Page 225
Common Typos and Syntax Problems......Page 226
Summary......Page 227
Appendix 1: Example Database......Page 228
Introduction......Page 230
Relations, Tuples, and Attributes......Page 231
Relational Algebra: Specifying the Operations......Page 233
Select......Page 234
Combining Select and Project......Page 235
Cartesian Product......Page 236
Inner Join......Page 237
Union, Difference, and Intersection......Page 238
Division......Page 240
Free and Bound Variables......Page 242
Existential Quantifier and SQL......Page 243
Universal Quantifier and SQL......Page 245
Algebra......Page 246
Calculus......Page 247
Conclusion......Page 248
Index......Page 249