Category Archives: T-SQL

T-SQL Tuesday #87 – Fixing Old Problems with Shiny New Toys: STRING_SPLIT

tsql2sday-300x300Thanks to Matt Gordon (@atsqlspeed) for hosting this T-SQL Tuesday.

Splitting Strings in SQL

A problem that has plagued SQL developers through the years is splitting strings. Many techniques have been used as more capabilities were added to SQL Server including XML datatypes, recursive CTEs and even CLR. I have used XML datatype methods to solve the problem most often. So, without further ado…

T-SQL Function: STRING_SPLIT

I have previously highlighted this function in a webinar with Pragmatic Works as a Hidden Gem in SQL Server 2016. It was not announced with great fanfare, but once discovered, solves a very common problem.

Syntax

STRING_SPLIT(string, delimiter)

The STRING_SPLIT function will return a single column result set. The column name is “value”. The datatype will be NVARCHAR for strings that are NCHAR or NVARCHAR. VARCHAR is used for strings that are CHAR or VARCHAR types.

Example

DECLARE @csvString AS VARCHAR(100)
SET @csvString = 'Monday, Tuesday, Wednesday, Thursday, Friday'
SELECT value AS WorkDayOfTheWeek 
FROM STRING_SPLIT (@csvString, ',');

The initial example returns the follow results:#tsql2sday

value
Monday
 Tuesday
 Wednesday
 Thursday
 Friday

As you can see in the example, the results returned a leading space which was in the original string. The following example trims leading and trailing spaces.

DECLARE @csvString AS VARCHAR(100)
SET @csvString = 'Monday, Tuesday, Wednesday, Thursday, Friday'
SELECT LTRIM(RTRIM(value)) AS WorkDayOfTheWeek 
FROM STRING_SPLIT (@csvString, ',');

The cleaned example returns the follow results:

value
Monday
Tuesday
Wednesday
Thursday
Friday

Thanks again Matt for this opportunity to share an underrated, but really useful shiny new tool in SQL Server 2016.

SQL Saturday #492 Follow Up – A Window into Your Data

sqlsat492_web

Thanks for attending my session on window functions in TSQL. I hope you learned something you can take back and use in your projects or at your work. You will find an link to the session and code I used below. If you have any questions about the session post them in comments and I will try to get you the answers.

Questions and Comments

  1. Does RATIO_TO_REPORT exist in SQL Server? It is in Oracle.
    • Currently this function is not available in SQL Server
    • Here is the equivalent functionality using existing functions in SQL Server:
      • OrderAmt / SUM(OrderAmt) OVER (PARTITION BY OrderDate)
      • This example can use the source code I have referenced below. It uses the current value as the numerator and the sum by partition as the denominator. While not a simple function, the equivalent is still fairly simple using window functions to help.
  2. Demo issues with Azure SQL Database
    • During the session I ran into an issue with Azure SQL Database. It turns out that the following two functions are not supported there.
      • PERCENTILE_CONT
      • PERCENTILE_DISC

Slides, Code, and Follow Up Posts

The presentation can be found here: A Window into Your Data

The code was put into a Word document that you can get here: TSQL Window Function Code

This session is also backed by an existing blog series I have written.

T-SQL Window Functions – Part 1- The OVER() Clause

T-SQL Window Functions – Part 2- Ranking Functions

T-SQL Window Functions – Part 3: Aggregate Functions

T-SQL Window Functions – Part 4- Analytic Functions

Microsoft Resources:

SQL Saturday #486 Richmond – A Window Into Your Data

 

sqlsat486_web

Thanks for attending my session on window functions in TSQL. I hope you learned something you can take back and use in your projects or at your work. You will find an link to the session and code I used below. If you have any questions about the session post them in comments and I will try to get you the answers.

Questions

  1. Can an OVER clause be used in the WHERE clause?
    • No. The OVER clause can only be used in SELECT and ORDER BY clauses.
  2. Some follow up on ROWS and RANGE with context to CURRENT ROW.
    • We had a lot of discussion around this. In our examples below, RANGE aggregated all the data that fit into the ORDER BY clause. ROWS only referenced the row it was in. So, RANGE looks at everything that meets the criteria established by the PARTITION BY and ORDER BY clauses. ROWS is bound to the physical row.
    • Code examples:
      • OVER (PARTITION BY CustomerName ORDER BY OrderDate RANGE CURRENT ROW)
        • Summed two rows of data for the customer with the date. Both rows had the same date.
      • OVER (PARTITION BY CustomerName ORDER BY OrderDate ROWS CURRENT ROW)
        • Each row only contained the data for the row it was in.

Slides, Code, and Follow Up Posts

The presentation can be found here: A Window into Your Data

The code was put into a Word document that you can get here: TSQL Window Function Code

This session is also backed by an existing blog series I have written.

T-SQL Window Functions – Part 1- The OVER() Clause

T-SQL Window Functions – Part 2- Ranking Functions

T-SQL Window Functions – Part 3: Aggregate Functions

T-SQL Window Functions – Part 4- Analytic Functions

Microsoft Resources:

SQL Saturday #437–Boston BI Edition 2015–You Can Still Analyze Data with T-SQL

image3

Thanks for attending my session on analyzing data with TSQL. I hope you learned something you can take back and use in your projects or at your work. You will find an link to the session and code I used below. If you have any questions about the session post them in comments and I will try to get you the answers.

The presentation can be found here: Analyzing with TSQL

The code was put into a Word document that you can get here: Code to support the analysis with TSQL Sessions

This session is also backed by an existing blog series I have written.

T-SQL Window Functions – Part 1- The OVER() Clause

T-SQL Window Functions – Part 2- Ranking Functions

T-SQL Window Functions – Part 3: Aggregate Functions

T-SQL Window Functions – Part 4- Analytic Functions

Microsoft Resources:

SQL Saturday #453–Minnesota 2015–A Window Into Your Data

image

Thanks for attending my session on window functions in TSQL. I hope you learned something you can take back and use in your projects or at your work. You will find an link to the session and code I used below. If you have any questions about the session post them in comments and I will try to get you the answers.

The presentation can be found here: A Window into Your Data

The code was put into a Word document that you can get here: TSQL Window Function Code

This session is also backed by an existing blog series I have written.

T-SQL Window Functions – Part 1- The OVER() Clause

T-SQL Window Functions – Part 2- Ranking Functions

T-SQL Window Functions – Part 3: Aggregate Functions

T-SQL Window Functions – Part 4- Analytic Functions

Microsoft Resources: