SQL Eval Function Overview

Definition

Eval SQL.NET is a library that allows to evaluate dynamically C# expression directly in T-SQL. You never used Eval SQL.NET? Don't worry, this step-by-step walkthrough will help you understand the library.

Provide to your SQL Server all missing pieces like regular expression and dynamic arithmetic string evaluation.

-- SELECT 3
SELECT  SQLNET::New('x+y').ValueInt('x', 1).ValueInt('y', 2).EvalInt() as Result

Installing

Download the SQLNET.zip

SQL Server 2017 - prerequisite

  1. Open the script SQLNET-Cert.sql
  2. Run the script
  3. Continue the install with next step

SQL Server 2008 or higher

  1. Open the script SQLNET-Install.sql
  2. Replace '[DATABASE_NAME]' with your database name
  3. Run the script

Note

  • For EXTERNAL_ACCESS PERMISSION

    • Uncomment "ALTER DATABASE [DATABASE_NAME] SET TRUSTWORTHY ON"
    • Uncomment "WITH PERMISSION_SET = EXTERNAL_ACCESS"
    • Comment "WITH PERMISSION_SET = SAFE"

  • For UNSAFE PERMISSION

    • Uncomment "ALTER DATABASE [DATABASE_NAME] SET TRUSTWORTHY ON"
    • Uncomment "WITH PERMISSION_SET = UNSAFE"
    • Comment "WITH PERMISSION_SET = SAFE"

Requirements

Minimus Requirements

  • SQL Server 2012+
  • SAFE Permission (SQL CLR)

Find your solutions:

  • Dynamic Arithmetic Expression
  • Dynamic Pivot Table
  • Regular Expression
  • String Interpolation
  • Replace xp_cmdshell with DirectoryInfo & FileInfo

Performance & Scalability

Performance tuning is one of the most important task for a DBA. Don't miss the chance to dramatically improve query performance by 300% for simple expression and by more than 2000% for complex code over User-Defined Function (UDF) and Table-Valued Function (TVF).

Methods 1,000 rows 10,000 rows 100,000 rows 1,000,000 rows
Eval-SQL.NET 4 ms 13 ms 160 ms 1,650 ms
fn_split (TVF) 100 ms 625 ms 5,500 ms 55,000 ms

Benchmark to split string with delimiters in SQL

Evaluate dynamic arithmetic/math expression in SQL

Make the impossible now possible. Evaluate C# expression in SQL to overcome limitations.

  • Allow trusted users to create report field and filter
  • Consume Web Service
  • Replace text in template with String Interpolation

Dynamic Expression Example

-- CREATE test
DECLARE @table TABLE ( X INT, Y INT, Z INT )
INSERT  INTO @table VALUES  ( 2, 4, 6 ),  ( 3, 5, 7 ), ( 4, 6, 8 )

-- Result: 14, 22, 32
DECLARE @sqlnet SQLNET = SQLNET::New('x*y+z')
SELECT  @sqlnet.ValueInt('x', X)
               .ValueInt('y', Y)
               .ValueInt('z', Z)
               .EvalInt() as Result
FROM    @table

Split text with delimiter

Improve performance and capability for splitting text with an easy to use split function and LINQ expression

  • Split text with multiple delimiters
  • Split text using a regular expression
  • Include row index

Split Text Example

-- CREATE test
DECLARE @t TABLE (Id INT , Input VARCHAR(MAX))
INSERT  INTO @t VALUES  ( 1, '1, 2, 3; 4; 5' ), ( 2, '6;7,8;9,10' )

-- SPLIT with many delimiters: ',' and ';'
DECLARE @sqlnet SQLNET = SQLNET::New('Regex.Split(input, ",|;")')

SELECT  *
FROM    @t AS A
        CROSS APPLY ( SELECT    *
                      FROM      dbo.SQLNET_EvalTVF_1(@sqlnet.ValueString('input', Input))
                    ) AS B

Use regular expression in SQL Server

Use Regex flexibility to overcome "LIKE" and "PATINDEX" limitations.

  • IsMatch
  • Match
  • Matches
  • Replace
  • Split

Regular Expression Example

DECLARE @customer TABLE ( Email VARCHAR(255) )

INSERT  INTO @customer
VALUES  ( 'info@zzzprojects.com' ),
        ( 'invalid.com' ),
        ( 'sales@zzzprojects.com' )

DECLARE @valid_email SQLNET = SQLNET::New('Regex.IsMatch(email, 
@"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$")')

-- SELECT 'invalid.com'
SELECT * FROM @customer WHERE @valid_email.ValueString('email', Email).EvalBit() = 0

Replace xp_cmdshell with restrictive alternative

Avoid enabling xp_cmdshell and compromising your SQL Server and use instead a more restrictive solution.

  • Impersonate Context
  • Improve maintainability
  • Improve readability
  • Improve security

Example

-- REQUIRE EXTERNAL_ACCESS permission
DECLARE @sqlnet SQLNET = SQLNET::New('
string path = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);

var dir = new DirectoryInfo(path);
return dir.GetFiles("*.*")
          .Select(x => new { x.FullName, FileContent = File.ReadAllText(x.FullName) })
          .OrderBy(x => x.FullName)')*9*
          .Impersonate()

-- SELECT FullName, FileContext FROM DesktopFiles ORDER BY Fullname
EXEC dbo.SQLNET_EvalResultSet @sqlnet

Contribute

The best way to contribute is by spreading the word about the library:

  • Blog it
  • Comment it
  • Fork it
  • Star it
  • Share it

A HUGE THANKS for your help.



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