Sql query - getting rid of hard-coded values

Question

I have the following query:

Select Name,
       case when charindex('I',a.S_Data) > 0 then 1 else 0 end as Illustrated,
       case when charindex('FP',a.S_Data) > 0 then 1 else 0 end as FrontPage,
       case when charindex('BP',a.S_Data) > 0 then 1 else 0 end as BackPage,
       case when charindex('ELP',a.S_Data) > 0 then 1 else 0 end as EDLP,
       case when charindex('PR',a.S_Data) > 0 then 1 else 0 end as SpecialPromo
From Table1

What I would like to do is to store those filter values in some sort of lookup table or a settings table.

I am struggling with how to draw the values from a lookup table to use with this query.

Answer 1

I can think of at least two options...

CREATE TABLE constants (
  id               AS INT,
  Illustrated      AS VARCHAR(3),
  FrontPage        AS VARCHAR(3),
  BackPage         AS VARCHAR(3),
  EDLP             AS VARCHAR(3),
  SpecialPromo     AS VARCHAR(3)
)

INSERT INTO constants SELECT 1, 'I', 'FP', 'BP', 'ELP', 'PR'

SELECT
  Name,
  CASE WHEN CHARINDEX(constants.Illustrated, data.S_Data) > 0 THEN 1 ELSE 0 END   AS Illustrated,
  etc, etc
FROM
  data
INNER JOIN
  constants
    ON constants.id = 1

Or...

CREATE TABLE constants (
  constant_set_id  AS INT,
  constant_name    AS VARCHAR(16),
  value            AS AS VARCHAR(3)
)

INSERT INTO constants SELECT 1, 'Illustrated',  'I'
INSERT INTO constants SELECT 1, 'FrontPage',    'FP'
INSERT INTO constants SELECT 1, 'BackPage',     'BP'
INSERT INTO constants SELECT 1, 'EDLP',         'ELP'
INSERT INTO constants SELECT 1, 'SpecialPromo', 'PR'

SELECT
  Name,
  MAX(CASE WHEN constants.constant_name = 'Illustrated' AND CHARINDEX(constants.value, data.S_Data) > 0 THEN 1 ELSE 0 END)   AS Illustrated,
  etc, etc
FROM
  data
INNER JOIN
  constants
    ON constants.constant_set_id = 1
GROUP BY
  data.name

Both let you have multiple different sets of constants. One is expandable without changing the schema, though the query still would need to change.

The main advantage of either approach is that you can re-use the constants else where, but store them once in a centralised location. Which is only relevant if/when the values in the constants needs updating. Re-use through indirection.