String Expression to be evaluated to number

Question

I need to write a TSQL user defined function which will accept a string and return a number.

I will call the function like dbo.EvaluateExpression(\'10*4.5*0.5\

Answer 1

Disclaimer: I'm the owner of the project Eval SQL.NET

For SQL 2012+, you can use Eval SQL.NET which can be run with SAFE Permission.

The performance is great (better than UDF) and honors operator precedence and parenthesis. In fact, almost all the C# language is supported.

You can also specify parameters to your formula.

-- SELECT 225.00
SELECT 10 * CAST(SQLNET::New('10*4.5*0.5').Eval() AS DECIMAL(18, 2))

-- SELECT 70
DECLARE @formula VARCHAR(50) = 'a+b*c'
SELECT  10 * SQLNET::New(@formula)
                    .Val('a', 1)
                    .Val('b', 2)
                    .Val('c', 3)
                    .EvalInt()