SQL Server T-SQL Recipes. Andy Roberts Wayne Sheffield. A Problem-Solution Approach. Jonathan Gennick. Jason Brimhall David Dye

Transcription

1 SQL Server 2012 T-SQL Recipes A Problem- Approach v? Jason Brimhall David Dye Jonathan Gennick Andy Roberts Wayne Sheffield

2 Contents About the Authors About the Technical Reviewers Acknowledgments Introduction <xlix II liii»lv Chapter 1: Getting Started with SELECT Connecting to a Database Retrieving Specific Columns , Retrieving All Columns Specifying the Rows to Be Returned Renaming the Output Columns Building a Column from an Expression v

3 IS CONTENTS 1-7. Providing Shorthand Names for Tables Negating a Search Condition Specifying A Range of Values How ItWorks Checking for NULL Values Providing a List of Values Performing Wildcard Searches Sorting Your Results Specifying Sort Order How ItWorks Sorting by Columns Not Selected Forcing Unusual Sort Orders vi

4 CONTENTS Paging Through A Result Set, Chapter 2: Elementary Programming..., Declaring Variables 23, Retrieving a Value into a Variable Writing an IF...THEN...ELSE Statement Writing a Simple CASE Expression Writing a Searched CASE Expression Writing a WHILE Statement Returning from the Current Execution Scope 32 #1: Exit with No Return Value 33 #2: Exit and Provide a Value Going to a Label in atransact-sql Batch vii

5 Jl CONTENTS 2-9. Pausing Execution for a Period of Time Creating and Using Cursors Chapter 3: NULLs and Other Pitfalls Replacing NULL with an Alternate Value Returning the First Non-NULL Value from a List Choosing Between ISNULL and COALESCE in a SELECT Statement Looking for NULLs in a Table Removing Values from an Aggregate Enforcing Uniqueness with NULL Values Enforcing Referential Integrity on Nuliable Columns Joining Tables on Nuliable Columns viii 55

6 11 CONTENTS Chapter4: Querying from Multiple Tables Correlating Parent and Child Rows Querying Many-to-Many Relationships Making One Side of a Join Optional Making Both Sides of a Join Optional Generating Ail Possible Row Combinations Selecting from a Result Set Testing for the Existence of a Row Testing Against the Result from a Query Comparing Subsets of a Table Stacking Two Row Sets Vertically ix

7 CONTENTS Eliminating Duplicate Values from a Union 70..., Subtracting One Row Set from Another Finding Rows in Common Between Two Row Sets Finding Rows That Are Missing Comparing Two Tables Chapter 5: Grouping and Summarizing., Summarizing a Result Set Creating Summary Groups Restricting a Result Set to Groups of Interest Removing Duplicates from the Detailed Results Creating Summary Cubes x

8 CONTENTS 5-6. Creating Hierarchical Summaries Creating Custom Summaries Identifying Rows Generated by the GROUP BY Arguments Identifying Summary Levels Chapter 6: Advanced Select Techniques Avoiding Duplicate Results 93 #1 93 # Returning the Top WRows Renaming a Column in the Output Retrieving Data Directly into Variables Creating a New Table with the Results from a Query xi

9 CONTENTS 6-6. Filtering on the Results from a Subquery Selecting from the Results of Another Query How ItWorks Passing Rows Through a Function Returning Random Rows from a Table Converting Rows into Columns Converting Columns into Rows Reusing Common Subqueries in a Query Querying Recursive Tables Hard-Coding the Results from a Query Chapter 7: Aggregations and Windowing Computing an Average xii

10 CONTENTS 7-2. Counting the Rows in a Group, Summing the Values in a Group 118 Summary Finding the High and Low Values in a Group Detecting Changes in a Table Finding the Statistical Variance in the Values of a Column Finding the Standard Deviation in the Values of a Column Calculating Totals Based Upon the Prior Row Calculating Totals Based Upon a Subset of Rows Using a Logical Window Generating an Incrementing Row Number xiii

11 ! CONTENTS Returning Rows by Rank Returning Rows by Rank Without Gaps Sorting Rows into Buckets Grouping Logically Consecutive Rows Together Accessing Values from Other Rows Accessing the First or Last Value from a Partition Calculating the Relative Position or Rank of a Value in a Set of Values Calculating Continuous or Discrete Percentiles Assigning Sequences in a Specified Order Chapter 8: Inserting, Updating, Deleting Inserting a New Row xiv

12 II CONTENTS 8-2. Specifying Default Values, 149, Overriding an IDENTITY Column Generating a Globally Unique Identifier (GUID) Inserting Results from a Query Inserting Results from a Stored Procedure Inserting Multiple Rows at Once Inserting Rows and Returning the Inserted Rows Updating a Single Row or Set of Rows Updating with a Second Table as the Data Source Updating Data and Returning the Affected Rows XV

13 1 CONTENTS Updating Large-Value Columns, , Deleting Rows Deleting Rows and Returning the Deleted Rows Deleting All Rows Quickly (Truncating) Merging Data (Inserting, Updating, or Deleting Values) Chapter 9: Working with Strings Concatenating Multiple Strings How it Works Finding a Character's ASCII Value How it Works Returning Integer and Character Unicode Values How it Works Locating a Substring How it Works Determining the Similarity of Strings How it Works 185 xvi

14 CONTENTS 9-6. Returning the Left-Most Portion of a String How it Works Returning Part of a String 187 How it Works Counting Characters or Bytes in a String How it Works Replacing Part of a String How it Works Stuffing a String into a String How it Works Changing Between Lower- and Uppercase How it Works Removing Leading and Trailing Blanks How it Works Repeating an Expression N Times How it Works Repeating a Blank Space N Times How it Works Reversing the order of Characters in a String How it Works 195 xvii

15 II CONTENTS Chapter 10: Working with Dates and Times Returning the Current Date and Time Converting Between Time Zones Converting a Date/Time Value to a Datetimeoffset Value Incrementing or Decrementing a Date's Vafue 200, Finding the Difference Between Two Dates Finding the Elapsed Time Between Two Dates How it Works Displaying the String Value for Part of a Date Displaying the Integer Representations for Parts of a Date Determining Whether a String Is a Valid Date How it Works Determining the Last Day of the Month xviii 206

16 I! CONTENTS Creating a Date from Numbers Finding the Beginning Date of a Datepart 207 #1 208 #2 209 #3 209 #1 210 #2 210 # Include Missing Dates Finding Arbitrary Dates Querying for Intervals Working with Dates and Times Across National Boundaries Chapter 11: Working with Numbers Representing Integers Representing Decimal Amounts xix

17 II CONTENTS Representing Monetary Amounts 222 #1 222 # Representing Floating-Point Values Writing Mathematical Expressions HOW It Works Guarding Against Errors in Expressions with Mixed Data Types How it Works Rounding, Rounding Always Up or Down Discarding Decimal Places Testing Equality of Binary Floating-Point Values Treating Nulls as Zeros Generating a Row Set of Sequential Numbers xx

18 II CONTENTS Generating Random Integers in a Row Set Reducing Space Used by Decimal Storage Chapter 12: Transactions, Locking, Blocking, and Deadlocking 241 Transaction Control Using Explicit Transactions Displaying the Oldest Active Transaction How ItWorks Querying Transaction Information by Session , 249 Locking Viewing Lock Activity Controlling a Table's Lock Escalation Behavior How ItWorks 255 Transaction, Locking, and Concurrency Configuring a Session's Transaction Locking Behavior Blocking 261 xxi

19 II CONTENTS Identifying and Resolving Blocking Issues Configuring How Long a Statement Will Wait for a Lock to Be Released Deadlocking Identifying Deadlocks with a Trace Flag Setting Deadlock Priority Chapter 13: Managing Tables Creating a Table Adding a Column Adding a Column That Requires Data Changing a Column Creating a Computed Column Removing a Column 276 xxii

20 II CONTENTS Removing a Table , Reporting on a Table's Definition Reducing Storage Used by NULL Columns Adding a Constraint to a Table Creating a Recursive Foreign Key Allowing Data Modifications to Foreign Keys Columns in the Referenced Table to Be Reflected in the Referencing Table Specifying Default Values for a Column Validating Data as It Is Entered into a Column Temporarily Turning Off a Constraint Removing a Constraint How ItWorks xxiii

21 a CONTENTS Creating Auto-incrementing Columns Obtaining the Identity Value Used Viewing or Changing the Seed Settings on an Identity Column Inserting Values into an Identity Column Automatically Inserting Unique Values Using Unique Identifiers Across Multiple Tables Using Temporary Storage 298 #1 298 # Chapter 14: Managing Views 301 Regular Views Creating a View Querying a View's Definition xxiv

22 B! CONTENTS Obtaining a List of All Views in a Database Obtaining a List of All Columns in a View Refreshing the Definition of a View Modifying a View Modifying Data Through a View Encrypting a View Indexing a View Creating a Partitioned View Creating a Distributed Partitioned View 318 ; Chapter 15: Managing Large Tables and Databases Partitioning a Table XXV

23 1 CONTENTS Locating Data in a Partition Adding a Partition Removing a Partition Determining Whether a Table Is Partitioned Determining the Boundary Values for a Partitioned Table Determining the Partitioning Column for a Partitioned Table Moving a Partition to a Different Partitioned Table Moving Data from a Nonpartitioned Table to a Partition in a Partitioned Table Moving a Partition from a Partitioned Table to a Nonpartitioned Table How ItWorks Reducing Table Locks on Partitioned Tables xxvi

24 8 CONTENTS Removing Partition Functions and Schemes Easing VLDB Manageability (with Filegroups) Compressing Table Data Rebuilding a Heap Chapter 16: Managing Indexes 341 Index Overview Creating a Table Index Enforcing Uniqueness on Non-key Columns Creating an Index on Multiple Columns 346, 347 How ItWorks Defining Index Column Sort Direction Viewing Index Metadata xxvii

25 II CONTENTS Disabling an Index Dropping Indexes Changing an Existing Index Controlling Index Build Performance and Concurrency Sorting in Tempdb Controlling Index Creation Parallelism User Table Access During Index Creation Index Options Using an Index INCLUDE Using PADINDEX and FILLFACTOR Disabling Page and/or Row Index Locking Managing Very Large Indexes 358 xxviii

26 II CONTENTS Creating an Index on a Filegroup Implementing Index Partitioning How ItWorks Indexing a Subset of Rows Reducing Index Size Chapter 17: Stored Procedures Selling the Benefits Creating a Stored Procedure Generalizing a Stored Procedure Making Parameters Optional Making Early Parameters Optional Returning Output How ItWorks 371 xxix

27 IS CONTENTS Modifying a Stored Procedure Removing a Stored Procedure How ItWorks Automatically Run a Stored Procedure at Start-Up Viewing a Stored Procedure's Definition Documenting Stored Procedures Determining the Current Nesting Level Encrypting a Stored Procedure 377., 378 How ft Works Specifying a Security Context Avoiding Cached Query Plans Flushing the Procedure Cache XXX

28 a CONTENTS Chapter 18: User-Defined Functions and Types UDF Basics Creating Scalar Functions Creating Inline Functions Creating Multi-Statement User-Defined Functions Modifying User-Defined Functions Viewing UDF Metadata Benefitting from UDFs Maintaining Reusable Code Cross-Referencing Natural Key Values 399 Problem How ItWorks Replacing a View with a Function Dropping a Function xxxi

29 CONTENTS UDT Basics Creating and Using User-Defined Types Identifying Dependencies on User-Defined Types Passing Table-Valued Parameters How ItWorks Dropping User-Defined Types Chapter 19: Triggers Creating an AFTER DML Trigger Creating an INSTEAD OF DML Trigger Handling Transactions in Triggers Linking Trigger Execution to Modified Columns Viewing DML Trigger Metadata Creating a DDL Trigger 430 xxxii

30 II CONTENTS Creating a Logon Trigger Viewing DDL Trigger Metadata 436, Modifying a Trigger Enabling and Disabling a Trigger Nesting Triggers Controlling Recursion How ItWorks Specifying the Firing Order Dropping a Trigger Chapter 20: Error Handling Handling batch errors,, xxxiii

31 a CONTENTS What are the error numbers and messages within SQL? How can I implement structured error handling in my queries? How can I use structured error handling, but still return an error? Nested error handling Throwing an error 457 #1: Use RAISERROR to throw an error #2: Use THROW to throw an error Creating a user defined error 461 : Use sp_addmessage to create user defined error message 461 How it Works Removing a user defined error 463 : Use sp_dropmessage to remove the user defined error message Chapter 21: Query Performance Tuning 465 Query Performance Tips 466 Capturing and Evaluating Query Performance Capturing Executing Queries xxxiv

32 II CONTENTS Viewing Estimated Query Execution Plans , Viewing Execution Runtime Information Viewing Statistics for Cached Plans How ItWorks Viewing Record Counts for Cached Plans Viewing Aggregated Performance Statistics Based on Query or Plan Patterns Identifying the Top Bottleneck Identifying I/O Contention by Database and File Miscellaneous Techniques Parameterizing Ad Hoc Queries Forcing Use of a Query Plan, Applying Hints Without Modifying a SQL Statement XXXV

33 a CONTENTS Creating Plan Guides from Cache Checking the Validity of a Plan Guide Parameterizing a Nonparameterized Query Using Plan Guides Limiting Competing Query Resource Consumption Chapter 22: Hints Forcing a Join's Execution Approach Forcing a Statement Recompile Executing a Query Without Locking 510 #1: The NOLOCK Hint 511 #2: The Isolation Level Forcing an Index Seek Forcing an Index Scan Optimizing for First Rows xxxvi

34 m CONTENTS Specifying Join Order Forcing Use of a Specific Index Optimizing for Specific Parameter Values Chapter 23: Index Tuning and Statistics, 519 Index Tuning Index Maintenance, Displaying Index Fragmentation How ItWorks Rebuilding Indexes Defragmenting Indexes Rebuilding a Heap Displaying Index Usage Statistics Manually Creating Statistics xxxvii

35 a CONTENTS Creating Statistics on a Subset of Rows Updating Statistics Generating Statistics Across All Tables Updating Statistics Across All Tables Viewing Statistics Details Removing Statistics 538 Chapter 24: XML, Creating an XML Column 539 How ft Works Inserting XML Data 540 How it Works Validating XML Data 542 How it Works Verifying the Existence of XML Schema Collections 545 xxxviii

36 CONTENTS Retrieving XML Data Modifying XML Data , Indexing XML Data How ItWorks Formatting Relational Data as XML 550, Formatting XML Data as Relational 555, 555 Chapter 25: Files, Filegroups, and Integrity Adding a Data File or a Log File Removing a Data File or a Log File Relocating a Data File or a Log File Changing a File's Logical Name Increasing the Size of a Database File xxxix

37 CONTENTS Adding a Filegroup Adding a File to a Filegroup Setting the Default Filegroup Adding Data to a Specific Filegroup Moving Data to a Different Filegroup 568 #1 568 #2 568 # Removing a Filegroup Making a Database or a Filegroup Read-Only 570 Problem #2 571 #1 571 # Viewing Database Space Usage 572 #1 572 #2 572 #3 573 How ItWorks 573 xl

38 a CONTENTS Shrinking the Database or a Database File 574 #1 574 # , Checking Consistency of Allocation Structures Checking Allocation and Structural Integrity Checking Integrity of Tables in a Filegroup Checking Integrity of Specific Tables and Indexed Views Checking Constraint Integrity Checking System Table Consistency Chapter 26: Backup < Backing Up a Database Compressing a Backup Ensuring That a Backup Can Be Restored xli

39 CONTENTS Understanding Why the Transaction Log Continues to Grow Performing a Differential Backup Backing Up a Single Row or Table 610 #1: Restore Rows from a Backup #2: Restore Rows from a Database Snapshot Backing Up Data Files or Filegroups 616 #1: Perform a File Backup 616 #2: Perform a Filegroup Backup Mirroring Backup Files Backing Up a Database Without Affecting the Normal Sequence of Backups Querying Backup Data Chapter 27: Recovery Restoring a Database from a Full Backup Restoring a Database from a Transaction Log Backup xlii

40 a CONTENTS Restoring a Database from a Differential Backup How ItWorks Restoring a File or Filegroup Performing a Piecemeal (PARTIAL) Restore Restoring a Page Identifying Databases with Multiple Recovery Paths Chapter 28: Principals and Users Windows Principals Creating a Windows Login Viewing Windows Logins How ItWorks Altering a Windows Login Dropping a Windows Login Denying SQL Server Access to a Windows User or Group xliii

41 CONTENTS SQL Server Principals Creating a SQL Server Login How St Works Viewing SQL Server Logins Altering a SQL Server Login Managing a Login's Password Dropping a SQL Login Managing Server Role Members Reporting Fixed Server Role Information Database Principals Creating Database Users Reporting Database User Information How it Works Modifying a Database User 659 xliv

42 CONTENTS Removing a Database User from the Database Fixing Orphaned Database Users Reporting Fixed Database Roles Information Managing Fixed Database Role Membership Managing User-Defined Database Roles Managing Application Roles Chapter 29: Securables, Permissions, and Auditing 673 Permissions Overview Reporting SQL Server Assignable Permissions Server-Scoped Securables and Permissions Managing Server Permissions xlv

43 CONTENTS Querying Server-Level Permissions Database-Scoped Securables and Permissions Managing Database Permissions Querying Database Permissions Schema-Scoped Securables and Permissions Managing Schemas Managing Schema Permissions Object Permissions Managing Object Permissions Managing Permissions Across Securable Scopes Determining Permissions to a Securable Reporting Permissions by Securable Scope Changing Securable Ownership xlvi

44 H CONTENTS Allowing Access to Non-SQL Server Resources Auditing Activity of Principals Against Securables Defining Audit Data Sources Capturing SQL Instance-Scoped Events Capturing Database-Scoped Events Querying Captured Audit Data Managing, Modifying, and Removing Audit Objects Chapter 30: Objects and Dependencies Changing the Name of a Database Object Changing an Object's Schema Identifying Objert Dependencies How ItWorks 728 xlvii

45 «CONTENTS Identifying Referencing and Referenced Entities Viewing an Object's Definition Returning a Database Object's Name, Schema Name, and Object ID Index 737 xlviii