Joe Celko s SQL for Smarties - Advanced SQL Programming P2 potx

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CONTENTS



1.4.4 CREATE TRIGGER Statement 52
1.4.5 CREATE PROCEDURE Statement 53
1.4.6 DECLARE CURSOR Statement 53

2

Normalization 61

2.1 Functional and Multivalued Dependencies 64
2.2 First Normal Form (1NF) 64
2.2.1 Note on Repeated Groups 66
2.3 Second Normal Form (2NF) 70
2.4 Third Normal Form (3NF) 71
2.5 Elementary Key Normal Form (EKNF) 72
2.6 Boyce-Codd Normal Form (BCNF) 73
2.7 Fourth Normal Form (4NF) 75
2.8 Fifth Normal Form (5NF) 76
2.9 Domain-Key Normal Form (DKNF) 78
2.10 Practical Hints for Normalization 87
2.11 Key Types 88
2.11.1 Natural Keys 89
2.11.2 Artificial Keys 89
2.11.3 Exposed Physical Locators 89
2.11.4 Practical Hints for Denormalization 91

2.11.5 Row Sorting 93

3

Numeric Data in SQL 101

3.1 Numeric Types 101
3.1.1 BIT, BYTE, and BOOLEAN Data Types 104
3.2 Numeric Type Conversion 105
3.2.1 Rounding and Truncating 105
3.2.2 CAST() Function 107
3.3 Four-Function Arithmetic 108
3.4 Arithmetic and NULLs 109
3.5 Converting Values to and from NULL 110
3.5.1 NULLIF() Function 110
3.5.2 COALESCE() Function 111
3.6 Vendor Math Functions 113

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3.6.1 Number Theory Operators 113
3.6.2 Exponential Functions 116
3.6.3 Scaling Functions 116
3.6.4 Converting Numbers to Words 117

4

Temporal Data Types in SQL 119

4.1 Notes on Calendar Standards 119
4.2 SQL Temporal Data Types 123
4.2.1 Tips for Handling Dates, Timestamps, and Times 124
4.2.2 Date Format Standards 124
4.2.3 Handling Timestamps 125
4.2.4 Handling Times 127
4.3 Queries with Date Arithmetic 128
4.4 The Nature of Temporal Data Models 129
4.4.1 Temporal Duplicates 129
4.4.2 Temporal Databases 135
4.4.3 Temporal Projection and Selection 137
4.4.4 Temporal Joins 139
4.4.5 Modifying Valid-Time State Tables 145
4.4.6 Current Modifications 146
4.4.7 Sequenced Modifications 150
4.4.8 Nonsequenced Modifications 155
4.4.9 Transaction-Time State Tables 156
4.4.10 Maintaining the Audit Log 158
4.4.11 Querying the Audit Log 160
4.4.12 Modifying the Audit Log 164
4.4.13 Bitemporal Tables 164
4.4.14 Temporal Support in Standard SQL 167

5

Character Data Types in SQL 169

5.1 Problems with SQL Strings 170
5.1.1 Problems of String Equality 170

5.1.2 Problems of String Ordering 171
5.1.3 Problems of String Grouping 172
5.2 Standard String Functions 172

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CONTENTS



5.3 Common Vendor Extensions 174
5.3.1 Phonetic Matching 175
5.4 Cutter Tables 182

6

NULLs: Missing Data in SQL 185

6.1 Empty and Missing Tables 187
6.2 Missing Values in Columns 187
6.3 Context and Missing Values 189
6.4 Comparing NULLs 190
6.5 NULLs and Logic 190
6.5.1 NULLS in Subquery Predicates 191
6.5.2 Standard SQL Solutions 193
6.6 Math and NULLs 193
6.7 Functions and NULLs 193
6.8 NULLs and Host Languages 194
6.9 Design Advice for NULLs 195
6.9.1 Avoiding NULLs from the Host Programs 197

6.10 A Note on Multiple NULL Values 198

7

Multiple Column Data Elements 201

7.1 Distance Functions 201
7.2 Storing an IP Address in SQL 202
7.2.1 A Single VARCHAR(15) Column 203
7.2.2 One INTEGER Column 203
7.2.3 Four SMALLINT Columns 205
7.3 Currency and Other Unit Conversions 205
7.4 Social Security Numbers 206
7.5 Rational Numbers 209

8

Table Operations 211

8.1 DELETE FROM Statement 211
8.1.1 The DELETE FROM Clause 212
8.1.2 The WHERE Clause 212
8.1.3 Deleting Based on Data in a Second Table 216
8.1.4 Deleting within the Same Table 216

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8.1.5 Deleting in Multiple Tables without Referential Integrity 220

8.2 INSERT INTO Statement 221
8.2.1 INSERT INTO Clause 221
8.2.2 The Nature of Inserts 222
8.2.3 Bulk Load and Unload Utilities 223
8.3 The UPDATE Statement 223
8.3.1 The UPDATE Clause 223
8.3.2 The WHERE Clause 224
8.3.3 The SET Clause 225
8.3.4 Updating with a Second Table 226
8.3.5 Using the CASE Expression in UPDATEs 228
8.4 A Note on Flaws in a Common Vendor Extension 231
8.5 MERGE Statement 232

9

Comparison or Theta Operators 235

9.1 Converting Data Types 236
9.2 Row Comparisons in SQL 238

10

Valued Predicates 241

10.1 IS NULL Predicate 241
10.1.1 Sources of NULLs 242
10.2 IS [NOT]{TRUE | FALSE | UNKNOWN} Predicate 242
10.3 IS [NOT] NORMALIZED Predicate 244

11

CASE Expressions 247

11.1 The CASE Expression 247
11.1.1 The COALESCE() and NULLIF() Functions 251
11.1.2 CASE Expressions with GROUP BY 252
11.1.3 CASE, CHECK() Clauses and Logical Implication 253
11.1.4 Subquery Expressions and Constants 257
11.2 Rozenshtein Characteristic Functions 258

12

LIKE Predicate 261

12.1 Tricks with Patterns 262

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CONTENTS



12.2 Results with NULL Values and Empty Strings 264
12.3 LIKE Is Not Equality 264
12.4 Avoiding the LIKE Predicate with a Join 264
12.5 CASE Expressions and LIKE Predicates 266
12.6 SIMILAR TO Predicates 267
12.7 Tricks with Strings 269
12.7.1 String Character Content 269
12.7.2 Searching versus Declaring a String 270

12.7.3 Creating an Index on a String 270

13

BETWEEN and OVERLAPS Predicates 273

13.1 The BETWEEN Predicate 273
13.1.1 Results with NULL Values 274
13.1.2 Results with Empty Sets 274
13.1.3 Programming Tips 274
13.2 OVERLAPS Predicate 275
13.2.1 Time Periods and OVERLAPS Predicate 275

14

The [NOT] IN() Predicate 287

14.1 Optimizing the IN() Predicate 288
14.2 Replacing ORs with the IN() Predicate 292
14.3 NULLs and the IN() Predicate 293
14.4 IN() Predicate and Referential Constraints 295
14.5 IN() Predicate and Scalar Queries 297

15

EXISTS() Predicate 299

15.1 EXISTS and NULLs 300
15.2 EXISTS and INNER JOINs 302
15.3 NOT EXISTS and OUTER JOINs 303

15.4 EXISTS() and Quantifiers 304
15.5 EXISTS() and Referential Constraints 305
15.6 EXISTS and Three-Valued Logic 306

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16

Quantified Subquery Predicates 309

16.1 Scalar Subquery Comparisons 310
16.2 Quantifiers and Missing Data 311
16.3 The ALL Predicate and Extrema Functions 313
16.4 The UNIQUE Predicate 314

17

The SELECT Statement 317

17.1 SELECT and JOINs 317
17.1.1 One-Level SELECT Statement 317
17.1.2 Correlated Subqueries in a SELECT Statement 324
17.1.3 SELECT Statement Syntax 326
17.1.4 The ORDER BY Clause 328
17.2 OUTER JOINs 336
17.2.1 Syntax for OUTER JOINs 337
17.2.2 NULLs and OUTER JOINs 342
17.2.3 NATURAL versus Searched OUTER JOINs 344

17.2.4 Self OUTER JOINs 345
17.2.5 Two or More OUTER JOINs 346
17.2.6 OUTER JOINs and Aggregate Functions 348
17.2.7 FULL OUTER JOIN 349
17.2.8 WHERE Clause OUTER JOIN Operators 350
17.3 Old versus New JOIN Syntax 351
17.4 Scope of Derived Table Names 353
17.5 JOINs by Function Calls 354
17.6 The UNION JOIN 356
17.7 Packing Joins 358
17.8 Dr. Codd’s T-Join 359
17.8.1 The Croatian Solution 363
17.8.2 The Swedish Solution 364
17.8.3 The Colombian Solution 364

18

VIEWs, Derived Tables, Materialized Tables, and
Temporary Tables 369

18.1 VIEWs in Queries 370
18.2 Updatable and Read-Only VIEWs 371

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18.3 Types of VIEWs 373

18.3.1 Single-Table Projection and Restriction 373
18.3.2 Calculated Columns 373
18.3.3 Translated Columns 373
18.3.4 Grouped VIEWs 374
18.3.5 UNIONed VIEWs 375
18.3.6 JOINs in VIEWs 377
18.3.7 Nested VIEWs 377
18.4 How VIEWs Are Handled in the Database System 379
18.4.1 View Column List 379
18.4.2 VIEW Materialization 379
18.4.3 In-Line Text Expansion 380
18.4.4 Pointer Structures 382
18.4.5 Indexing and Views 383
18.5 WITH CHECK OPTION Clause 383
18.5.1 WITH CHECK OPTION as CHECK() Clause 388
18.6 Dropping VIEWs 389
18.7 TEMPORARY TABLE Declarations 390
18.8 Hints on Using VIEWs and TEMPORARY TABLEs 391
18.8.1 Using VIEWs 392
18.8.2 Using TEMPORARY TABLEs 392
18.8.3 Flattening a Table with a VIEW 393
18.9 Using Derived Tables 395
18.9.1 Derived Tables in the FROM clause 395
18.9.2 Derived Tables with a VALUES Constructor 397
18.10 Derived Tables in the WITH Clause 397

19

Partitioning Data in Queries 401

19.1 Coverings and Partitions 401
19.1.1 Partitioning by Ranges 402
19.1.2 Partition by Functions 403
19.1.3 Partition by Sequences 404
19.2 Relational Division 406
19.2.1 Division with a Remainder 408
19.2.2 Exact Division 409

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19.2.3 Note on Performance 410
19.2.4 Todd’s Division 410
19.2.5 Division with JOINs 413
19.2.6 Division with Set Operators 413
19.3 Romley’s Division 414
19.4 Boolean Expressions in an RDBMS 418
19.5 FIFO and LIFO Subsets 420

20

Grouping Operations 425

20.1 GROUP BY Clause 425
20.1.1 NULLs and Groups 427
20.2 GROUP BY and HAVING 427
20.2.1 Group Characteristics and the HAVING Clause 429
20.3 Multiple Aggregation Levels 431
20.3.1 Grouped VIEWs for Multiple Aggregation Levels 432

20.3.2 Subquery Expressions for Multiple
Aggregation Levels 433
20.3.3 CASE Expressions for Multiple Aggregation Levels 434
20.4 Grouping on Computed Columns 435
20.5 Grouping into Pairs 436
20.6 Sorting and GROUP BY 437

21

Aggregate Functions 439

21.1 COUNT() Functions 440
21.2 SUM() Functions 443
21.3 AVG() Functions 444
21.3.1 Averages with Empty Groups 446
21.3.2 Averages across Columns 448
21.4 Extrema Functions 449
21.4.1 Simple Extrema Functions 449
21.4.2 Generalized Extrema Functions 451
21.4.3 Multiple Criteria Extrema Functions 460
21.4.4 GREATEST() and LEAST() Functions 462
21.5 The LIST() Aggregate Function 465
21.5.1 The LIST() Function with a Procedure 466

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CONTENTS

21.5.2 The LIST() Function by Crosstabs 467
21.6 The PRD() Aggregate Function 468
21.6.1 PRD() Function by Expressions 469
21.6.2 The PRD() Aggregate Function by Logarithms 470
21.7 Bitwise Aggregate Functions 473
21.7.1 Bitwise OR Aggregate Function 474
21.7.2 Bitwise AND Aggregate Function 475

22

Auxiliary Tables 477

22.1 The Sequence Table 477
22.1.1 Enumerating a List 479
22.1.2 Mapping a Sequence into a Cycle 481
22.1.3 Replacing an Iterative Loop 483
22.2 Lookup Auxiliary Tables 485
22.2.1 Simple Translation Auxiliary Tables 487
22.2.2 Multiple Translation Auxiliary Tables 487
22.2.3 Multiple Parameter Auxiliary Tables 488
22.2.4 Range Auxiliary Tables 489
22.2.5 Hierarchical Auxiliary Tables 490
22.2.6 One True Lookup Table 491
22.3 Auxiliary Function Tables 493
22.3.1 Inverse Functions with Auxiliary Tables 495
22.3.2 Interpolation with Auxiliary Function Tables 504
22.4 Global Constants Tables 506

23

Statistics in SQL 509

23.1 The Mode 510
23.2 The AVG() Function 512
23.3 The Median 512
23.3.1 Date’s First Median 513
23.3.2 Celko’s First Median 514
23.3.3 Date’s Second Median 516
23.3.4 Murchison’s Median 516
23.3.5 Celko’s Second Median 517
23.3.6 Vaughan’s Median with VIEWs 519

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23.3.7 Median with Characteristic Function 520
23.3.8 Celko’s Third Median 522
23.3.9 Ken Henderson’s Median 526
23.4 Variance and Standard Deviation 527
23.5 Average Deviation 528
23.6 Cumulative Statistics 528
23.6.1 Running Totals 529
23.6.2 Running Differences 530
23.6.3 Cumulative Percentages 531
23.6.4 Rankings and Related Statistics 533
23.6.5 Quintiles and Related Statistics 537
23.7 Cross Tabulations 538
23.7.1 Crosstabs by Cross Join 542
23.7.2 Crosstabs by Outer Joins 543

23.7.3 Crosstabs by Subquery 544
23.7.4 Crosstabs by CASE Expression 545
23.8 Harmonic Mean and Geometric Mean 545
23.9 Multivariable Descriptive Statistics in SQL 546
23.9.1 Covariance 546
23.9.2 Pearson’s r 547
23.9.3 NULLs in Multivariable Descriptive Statistics 548

24

Regions, Runs, Gaps, Sequences, and Series 549

24.1 Finding Subregions of Size (n) 550
24.2 Numbering Regions 551
24.3 Finding Regions of Maximum Size 552
24.4 Bound Queries 557
24.5 Run and Sequence Queries 557
24.5.1 Filling in Sequence Numbers 560
24.6 Summation of a Series 562
24.7 Swapping and Sliding Values in a List 565
24.8 Condensing a List of Numbers 567
24.9 Folding a List of Numbers 567
24.10 Coverings 568