Create different format for a table - sql

Question

I have a table with over 500 columns, dynamically created and named by the user. New columns can be created by the user, but none can be deleted.
I was given the task to program a keyword search that searches through all columns for a specific string, and returns the ID of that record. As you can imagine, the query currently looks something like:
SELECT form_id FROM table_name WHERE col1 LIKE '%str%' OR col2 LIKE '%str%' or col3 LIKE '%str%'.. etc.
It is unbelievably slow. To combat this, I'm trying to create another table, where this data is stored in a different format like this:
form_id, col_name, value
1, 'col2', 'some random value'
1, 'col1', 'another random value'
And then searching using:
SELECT id FROM new_table_name WHERE value LIKE '%str%'
I can export all the data and format it, and insert it into the new table. But how would I go about keeping the new table updated? Is it possible to have triggers that automatically insert/update the new table when the original one is modified? Even though I don't know the column names before hand?

Answer 1

Another option just for fun
Declare #YourTable Table (EmpID int,EmpName varchar(50),Salary int,Location varchar(100))
Insert Into #YourTable Values
(1,'Arul',100,null)
,(2,'Jane',120,'New York')
If 2016+ use JSON
Select*
From #YourTable A
Where (Select A.* For JSON Path,Without_Array_Wrapper ) like '%Jane%'
If <2016 use XML
Select*
From #YourTable A
Where (Select A.* For XML Raw ) like '%Jane%'
Both would Return
EmpID EmpName Salary Location
2 Jane 120 New York
If you want an exact match you can quote the string as such '%"Jane"%'

Answer 2

You can construct the table by unpivoting the original table:
select t.form_id, v.col, v.value
from t cross apply
(values ('col1', col1), ('col2', col2), . . . ) v(col, value);
You can then keep it up-to-date with insert and delete triggers for existing data. Then you will need DDL triggers to handle users adding new columns.

Answer 3

Seems like you are looking for an EAV model.
Here is one approach that does NOT require you to list the 500 columns.
Full Disclosure: This is NOT recommended for HUGE tables. UNPIVOT is more performant.
Also note that if you DON'T want null values remove ,ELEMENTS XSINIL
Example
Declare #YourTable Table (EmpID int,EmpName varchar(50),Salary int,Location varchar(100))
Insert Into #YourTable Values
(1,'Arul',100,null)
,(2,'Jane',120,'New York')
Select Entity = A.EmpID
,C.*
From #YourTable A
Cross Apply ( values (cast((Select A.* for XML RAW,ELEMENTS XSINIL) as xml))) B(XMLData)
Cross Apply (
Select Attribute = a.value('local-name(.)','varchar(100)')
,Value = a.value('.','varchar(max)')
From B.XMLData.nodes('/row') as C1(n)
Cross Apply C1.n.nodes('./*') as C2(a)
) C
Returns
Entity Attribute Value
1 EmpID 1
1 EmpName Arul
1 Salary 100
1 Location <<-- NULL values display as an empty string ... see note regarding nulls
2 EmpID 2
2 EmpName Jane
2 Salary 120
2 Location New York
EDIT - If 2016+ ... JSON
Select A.[EmpID]
,Attribute = B.[Key]
,Value = B.[Value]
From #YourTable A
Cross Apply ( Select * From OpenJson((Select A.* For JSON Path,Without_Array_Wrapper )) ) B