SQL Find dynamic column and update value [closed] - sql

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I have 2 tables
##tblReports - temporary table
Books| GroupId | Category | 01-01-2014 | 02-01-2014 | ..etc
----------+------------+--------------------------
100 | 1 | Limit | 700 | 0
100 | 1 | Exp | 70 | 0
100 | 1 | Balance | 630 | 0
200 | 1 | Limit | 0 | 900
200 | 1 | Exp | 0 | 100
200 | 1 | Balance | 0 | 800
tblLimits -user table
GroupId | 100BooksLimit | 200BooksLimit
----------+------------+---------------
1 | 700 | 900
2 | 7 | 10
Desired output
Books| GroupId | Category | 01-01-2014 | 02-01-2014
----------+------------+--------------------------
100 | 1 | Limit | 700 | 700
100 | 1 | Exp | 70 | 0
100 | 1 | Balance | 630 | 700
200 | 1 | Limit | 900 | 900
200 | 1 | Exp | 0 | 100
200 | 1 | Balance | 900 | 800
the 3rd column onwards from ##tblReports are dynamic. Can you help me how to update it?
Basically:
find all the columns with 0 values
search for its limit in tblLimits table using GroupId and Books.
get the limit and update 'Limit' and 'Balance' row
I tried to use dynamic queries but I cant make it work. Please help me
*I know the design of the tables are not ideal and follow the best practices as this is a client requirement that I need to follow. This is a temporary table and a lot of things happened before this table (multiple joins, pivot and un-pivot)
tables shown are simplified and does not exactly replicate the actual table. Thanks!

Answer 1

-- Create temp tables and sample data
CREATE TABLE ##tblReports (books INT, groupid INT, category VARCHAR(25), [01-01-2014] INT, [02-01-2014] INT)
INSERT INTO ##tblReports VALUES (100, 1, 'Limit', 700, 0), (100, 1, 'Exp', 70, 0), (100, 1, 'Balance', 630, 0),
(200, 1, 'Limit', 0, 900), (200, 1, 'Exp', 0, 100), (200, 1, 'Balance', 0, 800)
CREATE TABLE ##tblLimits (groupid INT, [100bookslimit] INT, [200bookslimit] INT)
INSERT INTO ##tblLimits VALUES (1, 700, 900), (2, 7, 10)
-- Unpivot ##tblLimits in a CTE (see footnote for what this outputs)
DECLARE #sql NVARCHAR(MAX)
SELECT #sql = '
;WITH cte_unpivot AS
(
SELECT groupid, val, CAST(REPLACE(col, ''bookslimit'', '''') AS INT) AS books
FROM ##tblLimits
UNPIVOT (val FOR col IN ('
-- Are the columns in ##tblLimits dynamic (other than groupid)? If so, get their
-- names from tempdb.sys.columns metadata.
SELECT #sql += QUOTENAME(name) + ',' -- [Column],
FROM tempdb.sys.columns
WHERE [object_id] = OBJECT_ID(N'tempdb..##tblLimits') AND name <> 'groupid'
-- Delete trailing comma
SELECT #sql = SUBSTRING(#sql, 1, LEN(#sql) - 1)
SELECT #sql += '))AS u
)
SELECT t.books, t.groupid, category,
'
-- Get ##tblReports column names from tempdb.sys.columns metadata.
SELECT #sql += '
CASE WHEN ' + QUOTENAME(name) + ' = 0 AND t.category IN (''Limit'', ''Balance'')
THEN c.val ELSE t.' + QUOTENAME(name) + ' END AS ' + QUOTENAME(name) + ','
FROM tempdb.sys.columns
WHERE [object_id] = OBJECT_ID(N'tempdb..##tblReports') AND name NOT IN ('books', 'groupid', 'category')
-- Delete trailing comma again
SELECT #sql = SUBSTRING(#sql, 1, LEN(#sql) - 1)
SELECT #sql += '
FROM ##tblReports t
LEFT JOIN cte_unpivot c ON t.books = c.books AND t.groupid = c.groupid
'
EXEC sp_executesql #sql
Returns:
books groupid category 01-01-2014 02-01-2014
100 1 Limit 700 700
100 1 Exp 70 0
100 1 Balance 630 700
200 1 Limit 900 900
200 1 Exp 0 100
200 1 Balance 900 800
The key is unpivoting ##tblLimits into this format so you can easily join it to ##tblReports:
groupid val books
1 700 100
1 900 200
2 7 100
2 10 200
Here's the SQL it generates (but formatted):
;WITH cte_unpivot
AS (SELECT groupid,
val,
Cast(Replace(col, 'bookslimit', '') AS INT) AS books
FROM ##tbllimits
UNPIVOT (val
FOR col IN ([100bookslimit],
[200bookslimit]))AS u)
SELECT t.books,
t.groupid,
category,
CASE
WHEN [01-01-2014] = 0
AND t.category IN ( 'Limit', 'Balance' ) THEN c.val
ELSE t.[01-01-2014]
END AS [01-01-2014],
CASE
WHEN [02-01-2014] = 0
AND t.category IN ( 'Limit', 'Balance' ) THEN c.val
ELSE t.[02-01-2014]
END AS [02-01-2014]
FROM ##tblreports t
LEFT JOIN cte_unpivot c
ON t.books = c.books
AND t.groupid = c.groupid