Manipulating a Column Containing Key/Value Pairs

Question

I'm accessing and creating reports from a vendor via a replicated SQL Server database. They've done some absolutely insane things that I've been trying to solve for, but this one takes the cake.

They have a table that has many standard columns. But this table also has a column called "Data". The column is a legacy "text" data type, and it contains a giant (hundreds) list of key/value pairs. Each pair is separated by a CRLF, and the key and value are separated by an equal sign. Example:

select myTable.[data] from myTable where tblKey = 123

Result:

Key 1=Value 1
Key 2=Value 2
Key 3=Value 3
...
Key 500=Value 500

I'm trying to determine the most efficient way to break that column out into a usable table of data. The end goal would be to be able to query the table in a way that returns the table key along with specified key/values as column/fields as such:

tblKey | [Key 1] | [Key 3] | [Key 243]
-------|---------|---------|-----------
 123     Value 1   Value 3   Value 243
 124     Value 1   Value 3   Value 243
 125     Value 1   Value 3   Value 243

Is there a way to mold that column into a View? I can't imagine that a Function would be particularly efficient, but I'm sure I could parse things out that way using a string_split or something of that sort. Has anyone run into this type of atrocity before and found a good way to manipulate it into usable data?

Edit to add dbfiddle sample data.

The data is replicated from a vendor's source, so I can't create new tables. I can create views, procedures and functions. That's what I'm looking for advice for a decent way to accomplish.

Answer 1

UPDATE

If as you posted in your own answer you're able to use a UDF to get specific key values let me suggest this one: (You don't need to split all key/values and you don't need to read the table again, you can get it by using text functions.)

CREATE FUNCTION fnGetKey(@Data text, @Key varchar(20))
RETURNS varchar(100)
AS
BEGIN

  RETURN
  (
  SELECT 
      SUBSTRING (
                  @Data,
                  /* Position of first '=' after key + 1 */
                  CHARINDEX('=', @Data, PATINDEX('%' + @key + '%', @Data)) + 1,
                  /* Lenght, Position of first chr(13) after key less previuos value - 1 */
                  (CHARINDEX(CHAR(13), @Data, PATINDEX('%' + @key + '%', @Data)) 
                  - 
                  CHARINDEX('=', @Data, PATINDEX('%' + @key + '%', @Data))) - 1
                )
  )

END

SELECT
    FruitID, Name, Description,
    dbo.fnGetKey([Data], 'key 2') as [key 2],
    dbo.fnGetKey([Data], 'key 4') as [key 4]
FROM
    [Fruit];

FruitID | Name   | Description | key 2   | key 4  
------: | :----- | :---------- | :------ | :------
      1 | Banana | Delicious   | value 2 | value 4
      2 | Pear   | Rotton      | value 2 | value 4
      3 | Kiwi   | Okay        | value 2 | value 4

db<>fiddle here

Original answer

The only solution I can figure out is by splitting key/values and then pivot it to obtain the desired result.

Unfortunately there are some inconveniences:

• STRING_SPLIT doesn't works with text columns. Hence you must cast it to varchar before you are able to manipulate it.
• STRING_SPLIT requires a nchar(1) or nvarchar(1), ergo you should replace CHAR(3)+CHAR(10) by a single character.
• Aggregate function on PIVOT works better with numeric values, then you should cast Value to some numeric data type.
• PIVOT needs a well-known number of columns, in my example I have used a few of them but you should write the whole sequence unless you'd rather deal with dynamic queries.

This is what I've got using your sample data:

WITH KP AS
(
    SELECT FruitID, Name, Description, value as KPair
    FROM   Fruit
    CROSS APPLY STRING_SPLIT(REPLACE(CAST(Data AS varchar(max)), CHAR(13)+CHAR(10), ','), ',') /* STRING_SPLIT only allows nchar(1),  varchar(1) */
)
, KP1 AS
(
  SELECT
      FruitID,  
      SUBSTRING(KPair, 5, CHARINDEX('=', KPair) - 5) AS [Key],
      SUBSTRING(KPair, CHARINDEX('=', KPair) + 7, LEN(KPair) - CHARINDEX('=', KPair) - 6) AS [Value]
  FROM
      KP
)
SELECT [FruitID], [1],[2],[3],[4],[5]
FROM   KP1
PIVOT (MAX([Value]) FOR [Key] IN ([1],[2],[3],[4],[5])) AS PVT;

First CTE split every Key X=Value Y. The second one cut this value to obtain each [Key] and [Value]. And the final PIVOT compose the final result in columns.

FruitID | 1  | 2  | 3  | 4  | 5 
------: | :- | :- | :- | :- | :-
      1 | 1  | 2  | 3  | 4  | 5 
      2 | 1  | 2  | 3  | 4  | 5 
      3 | 1  | 2  | 3  | 4  | 5 

db<>fiddle here

NOTE: I'm not sure if I should maintain [Key 1] & [Value 1] or it should be converted as a column named [Key] & [Value].

A different approach

When I work with 3rd party databases I usually add a new database, on the same server/instance if possible, and then I use it for my own purposes, just to avoid conflicts with the DB owners.

In this case you could add a new table and periodically throw a process to update it with the new values.

You could use a table with all columns:

CREATE TABLE [FruitKeys]
(
    [FruitID] int NOT NULL PRIMARY KEY,
    [V1]      int NULL,
    [V2]      int NULL,
    [V3]      int NULL,
    [V4]      int NULL,
    [V5]      int NULL
);

or a table with Key/Value pairs and use a pivot to obtain the final result:

CREATE TABLE [FruitKeys]
(
    [FruitID] int NOT NULL,
    [Key]     int NOT NULL,
    [Value]   int NOT NULL,
    CONSTRAINT [PK_FruitKeys] PRIMARY KEY ([FruitID], [Key])
);

Answer 2

It seems to me that the source data is not that far from JSON format.

You could convert it pretty directly then use OPENJSON to produce a relational output:

SELECT
    F.FruitID,
    F.[Name],
    OJ.[key 1],
    OJ.[key 2],
    OJ.[key 3],
    OJ.[key 4],
    OJ.[key 5],
    F.[Description]
FROM dbo.Fruit AS F
CROSS APPLY OPENJSON
(
    -- Convert source data to JSON format
    '{' + 
        CHAR(34) + 
        REPLACE
        (
            REPLACE
            (
                CONVERT(varchar(max), F.Data), 
                '=', CHAR(34) + ':' + CHAR(34)
            ), 
            CHAR(13) + CHAR(10), 
            CHAR(34) + ',' + CHAR(34)
        ) + 
        CHAR(34) + 
    '}'
) 
WITH
(
    [key 1] varchar(100),
    [key 2] varchar(100),
    [key 3] varchar(100),
    [key 4] varchar(100),
    [key 5] varchar(100)
) AS OJ;

Output:

FruitID | Name   | key 1   | key 2   | key 3   | key 4   | key 5   | Description
------: | :----- | :------ | :------ | :------ | :------ | :------ | :----------
      1 | Banana | value 1 | value 2 | value 3 | value 4 | value 5 | Delicious  
      2 | Pear   | value 1 | value 2 | value 3 | value 4 | value 5 | Rotton     
      3 | Kiwi   | value 1 | value 2 | value 3 | value 4 | value 5 | Okay       

db<>fiddle demo

Answer 3

McNets provided a reasonable approach, but the splitting for every pair, while obviously necessary, is a pretty time consuming process. With 500+ key/value pairs for every record in the table, I'm not sure it's going to work for my purposes. It's probably a decent approach if there are fewer pairs and a small number of rows in the affected table.

Because I'm working with hundreds of key/value pairs and also thousands of records in the table itself, I'm thinking about implementing a user defined function (below) to use as-needed in reports and queries where a specific key/value pair is needed (and known).

CREATE FUNCTION udfsv_GetFruitDataValue(
    @FruitID int, 
    @DataId varchar(100)
)
RETURNS varchar(100)
AS BEGIN
  DECLARE @DataVal varchar(100)

  set @DataVal = (
    select 
      replace(replace(split1, @DataId + '=', ''), char(13), '') as DataValue
    from Fruit
    left outer join (
      select
        FruitID,
           value as split1
      from Fruit 
      cross apply string_split(cast([data] as varchar(max)), char(10))
    ) line1 on line1.FruitID = Fruit.FruitID         
    where Fruit.FruitID = @FruitID
    and split1 like @DataId + '=%'
  )

  RETURN @DataVal
END

With this I'd be able to perform queries to include specified key/values, just not all key/values.

SELECT
  FruitID,
  Name,
  Description,
  udfsv_GetFruitDataValue(FruitID, 'Key 1') as [Key 1],
  udfsv_GetFruitDataValue(FruitID, 'Key 4') as [Key 4]
FROM
  Fruit
WHERE FruitID = 123