How to write formulas based on text of columns in another table

Question

We have thousands of formulas stored in a table 'Formulas'. How can we calculate values from a data table 'D1' based on the formulas in 'Formulas'
Table 'D1' has columns:
V1 V2 V3 V4 V5
with standard numeric data.
Table 'Formulas' has columns Date and F1 with value such as
Date  F1
2013 'v1=v2+v3'
2014 'v1=v2*v5'
The formulas in 'Formulas' are date-specific and also can change over time, so the solution must be dynamically generated during execution.
Thanks!

Answer 1

If the table is relatively small, you may try:
IF object_id(N'TempDB..#D1') IS NOT NULL
DROP TABLE #D1;
CREATE TABLE #D1 (
Id INT identity(1, 1) PRIMARY KEY
,v1 DECIMAL(10, 2)
,v2 DECIMAL(10, 2)
,v3 DECIMAL(10, 2)
,v4 DECIMAL(10, 2)
,v5 DECIMAL(10, 2)
,formula VARCHAR(200)
INSERT INTO #D1 (
v1
,v2
,v3
,v4
,v5
,formula
VALUES (
10
,12
,14
,8
,3
,'v1=v2+v3'
7
,5
,3
,9
,4
,'v5=v1*v2'
DECLARE @sql NVARCHAR(max)
SET @sql = stuff((
SELECT ' UNION ALL
SELECT Id, ' + quotename(formula, '''') + ' AS Formula, ' + CASE left(formula, 3)
WHEN 'v1='
THEN substring(formula, 4, len(formula))
ELSE cast(v1 AS VARCHAR(30))
END + ' AS v1,' + CASE left(formula, 3)
WHEN 'v2='
THEN substring(formula, 4, len(formula))
ELSE cast(v2 AS VARCHAR(30))
END + ' AS v2,' + CASE left(formula, 3)
WHEN 'v3='
THEN substring(formula, 4, len(formula))
ELSE cast(v3 AS VARCHAR(30))
END + ' AS v3,' + CASE left(formula, 3)
WHEN 'v4='
THEN substring(formula, 4, len(formula))
ELSE cast(v4 AS VARCHAR(30))
END + ' AS v4,' + CASE left(formula, 3)
WHEN 'v5='
THEN substring(formula, 4, len(formula))
ELSE cast(v5 AS VARCHAR(30))
END + ' AS v5
FROM #D1 WHERE ID =' + cast(Id AS VARCHAR(30))
FROM #D1
FOR XML PATH('')
,TYPE
).value('.', 'varchar(max)'), 1, 12, '')
PRINT @SQL
EXECUTE (@SQL)
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