Tutorials
Practical T-SQL
Practical T-SQL
  • Practical T-SQL Pocket Guide For Beginners
  • Preface
    • Section I. A Note From The Author
    • Section II. Tutorial Overview
    • Section III. Running The Examples
    • Section IV. How To Report An Issue
    • Section V. Join The MSU Community On Discord
    • Section VI. Supplementary Material
  • Language Basics
    • Lesson 1. Obligatory Hello World
    • Lesson 2. Code Comments With T-SQL
    • Lesson 3. Basic Syntax
    • Lesson 4. Your First Query
    • Lesson 5. Filtering Data
    • Lesson 6. Sorting Data
    • Lesson 7. Complex Data Filtering
    • Lesson 8. Aliases
    • Lesson 9. String Functions
    • Lesson 10. Creating New Columns From Existing Data (Calculated Fields)
    • Lesson 11. Displaying Data Based On Conditions (Case Statement)
    • Lesson 12. Aggregate Functions
    • Lesson 13. Grouping And Summarizing Data
    • Lesson 14. Querying More Than One Table
    • Lesson 15. Combining Queries
    • Lesson 16. Subqueries
    • Lesson 17. Creating Data
    • Lesson 18. Updating Data
    • Lesson 19. Deleting Data
    • Lesson 20. Common Table Expressions (CTEs)
    • Lesson 21. Derived Tables
    • Lesson 22. Putting It All Together
  • Advanced Topics
    • Lesson 23. Selecting Unique Values
    • Lesson 24. Updating Data With A Join
    • Lesson 25. Data Types
    • Lesson 26. Casting Data Types
    • Lesson 27. Creating Tables
    • Lesson 28. Altering Tables
    • Lesson 29. Dropping Tables
    • Lesson 30. Variables
    • Lesson 31. Controlling Flow
    • Lesson 32. Looping
    • Lesson 33. Error Processing
    • Lesson 34. Temporary Tables
    • Lesson 35. Views
    • Lesson 36. Indexed Views
    • Lesson 37. User Defined Functions
    • Lesson 38. Stored Procedures
    • Lesson 39. BULK INSERT
    • Lesson 40. Loading Tables With MERGE
    • Lesson 41. Partitioning A Dataset
    • Lesson 42. Pivoting Data
    • Lesson 43. Dynamic SQL
    • Lesson 44. Cursors
  • Solutions To Real World Problems
    • Lesson 45. Listing All Tables In A SQL Server Database
    • Lesson 46. Listing All Columns In A SQL Server Database
    • Lesson 47. Pull Records From A Table At Random
    • Lesson 48. A Better Alternative To WITH (NOLOCK)
    • Lesson 49. Boost Performance When Calling A Stored Proc From SSIS
    • Lesson 50. Setting Up Queries For Ablation Testing
    • Lesson 51. Reduce Code And Save Time With Default Column Values
    • Lesson 52. Finding Duplicate Records In A Table
    • Lesson 53. Why You Cannot Have More Than One Clustered Index On A Table
    • Lesson 54. Converting Dates To YYYYMMDD
    • Lesson 55. Sending Notification Emails With T-SQL Without Using Hardcoded Email Addresses
    • Lesson 56. Troubleshooting Long Running Queries
    • Lesson 57. Loading Large CSVs Into Data Warehouse Staging Tables
    • Lesson 58. The Only Bloody Good Reason To Use Cursors
    • Lesson 59. Loading A Type II Slowly Changing Dimension With SQL Merge
    • Lesson 60. A Clearer Explanation Of The Parameters Of The Numeric Data Type
    • Lesson 61. Why You Cannot Join On Null Values
    • Lesson 62. A Deep Dive On How The Where Clause Functions
    • Lesson 63. Using HASHBYTES() To Compare Character Strings
    • Lesson 64. Using Pipe To Hash Multiple Columns For Matching
    • Lesson 65. Why People That Indent Code Drive Me Nuts
    • Lesson 66. How To Rapidly Stand Up A Data Warehouse From Scratch
    • Lesson 67. How To Pivot Data With T-SQL When Columns Are Not Predefined
    • Lesson 68. Prepopulating A Junk Dimension
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  1. Language Basics

Lesson 2. Code Comments With T-SQL

This is how you comment out code you do not want to run. There are two kinds of code comment techniques. Single line and multi-line.

Examples

Single And Multi-Line Comment

USE AdventureWorks2016

--This is a single line comment.

/*
This is a 
multi-line
comment.
*/

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