SQL Server : indexing for table and columns - sql-server

Question

I have a table where I am storing all tables name and column name, now I want to get data according to that table with different conditions.
I will use one single query column name and table name will take dynamically from this table and than I will use in select query and will get data from respective column and table.
Table name is ADE_ColumnIndexing
In this table I have all table names as TableName column, and column names as name column...
Now I want to use
select fieldname
from tablename
where Id = newdata
This query will return data of that column and table... I mean tablename = ade_log and columnname = history...
So my query will be select history from ade_log... Is it possible?

Answer 1

It's possible to build and execute dynamic sql, though it doesn't seem like a good aproach:
DECLARE #Sql varchar(max)
SELECT #Sql = 'SELECT '+ ColumnName +
' FROM '+ TableName +
' WHERE Id = '+ IdValue
FROM ADE_ColumnIndexing
WHERE TableName = #TableName
AND ColumnName = #ColumnName
EXEC(#Sql)

Answer 2

I think if you use the ID column for search, definitely not recommended as it may seem to me, the IDVal is auto-increment (correct me if i'm wrong). So why not use
exec('select [' + #column_name + '] from [' + #tablename + ']');
if you want an added validation if the table or column exists, you may query in sys.
if (
select
COUNT(*)
from sys.tables tb
left join sys.columns c
on
tb.object_id = c.object_id
where
tb.name = #tablename
and c.name = #columnname
) != 0
begin
exec('select [' + #column_name + '] from [' + #tablename + ']');
end
else
begin
select 'table or column does not exist'
end
EDIT : Seems like your table has "queries" as a row, then see my simple script below if I understand you correctly....(hopefully)
CREATE TABLE test (qry nvarchar(4000)) -- test query table
CREATE TABLE test1 (sales decimal(18,2)) -- sales table
INSERT INTO test1 (sales) -- dummy records for sales table
values (5923.59), (5923.52),(5923.51)
INSERT INTO test (qry) -- dummy records for query table
values ('select * from test1 where sales = 5923.59')
,('select * from test1 where sales = 5923.52')
,('select * from test1 where sales = 5923.51')
declare #myqry nvarchar(4000) = (SELECT qry + '; ' AS [text()] FROM test FOR XML PATH('')) -- from records to 1 query statement with multiple table results
declare #myqry2 nvarchar(4000) = SUBSTRING(
(SELECT qry + ' union all ' AS [text()] FROM test FOR XML PATH(''))
,0
,LEN((SELECT qry + ' union all ' AS [text()] FROM test FOR XML PATH(''))) - 9
)
-- from records to 1 query statement with single table results
select 'my query', #myqry -- see content of #myqry
select 'my query 2', #myqry2 -- see content of #myqry2
EXEC(#myqry) -- execute #myqry
EXEC(#myqry2) -- execute #myqry2
EDIT : This is my last attempt for your case. Please try this sample code set which still uses table:[test] and table:[test1]
DECLARE #intloop INT = 1 -- variable setter for number of loops
,#qry nvarchar(4000) = '' -- variable setter for the looping query
SELECT ROW_NUMBER() OVER (ORDER BY qry) AS id, qry INTO #tmpQueries FROM [test] -- create temp table for fake 'id'
CREATE TABLE #tmpQuery (id int, qry nvarchar(4000), res nvarchar(4000)) -- table result container
CREATE TABLE #tmpInsert (res nvarchar(4000)) -- execute query container
WHILE (#intloop < (SELECT COUNT(*) FROM #tmpQueries) + 1)
BEGIN
SET #qry = (SELECT TOP 1 qry FROM #tmpQueries WHERE id = #intloop) -- get the qry base from ID
DELETE FROM #tmpInsert -- delete records of query container
INSERT INTO #tmpInsert -- insert records into query container
EXEC (#qry) -- execute qry
INSERT INTO #tmpQuery (id, qry, res)
VALUES (#intloop, #qry, (SELECT TOP 1 res FROM #tmpInsert)) -- transfer id, qry and result into #tmpQuery table
SET #intloop = #intloop + 1 -- increment record
END
SELECT * FROM #tmpQuery -- select all records in #tmpQuery table
DROP TABLE #tmpQueries
DROP TABLE #tmpQuery
DROP TABLE #tmpInsert
NEW TABLE SAMPLE STRUCT : Create identity ID's for test and test1, and specify ID inside query. (notice the select * from test1 before into select id, sales from test1)
CREATE TABLE test (id int identity(1,1), qry nvarchar(4000)) -- test query table
CREATE TABLE test1 (id int identity(1,1), sales decimal(18,2)) -- sales table
INSERT INTO test1 (sales) -- dummy records for sales table
values (5923.59), (5923.52),(5923.51)
INSERT INTO test (qry) -- dummy records for query table
values
('select id, sales from test1 where sales = 5923.59')
,('select id, sales from test1 where sales = 5923.52')
,('select id, sales from test1 where sales = 5923.51')
SIMPLIFIED SCRIPT : Assuming all ID's of test and test1 are siblings, you can simply do the query this way.
declare #myqry2 nvarchar(4000) = SUBSTRING(
(SELECT qry + ' union all ' AS [text()] FROM test FOR XML PATH(''))
,0
,LEN((SELECT qry + ' union all ' AS [text()] FROM test FOR XML PATH(''))) - 9
)
CREATE TABLE #tmpResult(id int, qry nvarchar(4000))
INSERT INTO #tmpResult
EXEC(#myqry2) -- execute #myqry2
SELECT
tr.id
, t.qry
, tr.qry AS [sales]
FROM [test] t
LEFT JOIN #tmpResult tr
ON
t.id = tr.id
DROP TABLE #tmpResult
EDIT : We can remove the substring, but as per your request, all rows must be in single table result, so "union all" can't be un-done, unless you have your own ways, that's a plus.
select
*,
case
when id = 1 then ' union all '
when id = 2 then ' union all '
else ''
end as [row_extender]
into #tmptest
from test
--drop table #tmptest
declare #myqry2 nvarchar(4000) = (SELECT qry + row_extender AS [text()] FROM #tmptest FOR XML PATH(''))
CREATE TABLE #tmpResult(id int, qry nvarchar(4000))
INSERT INTO #tmpResult
EXEC(#myqry2) -- execute #myqry2
SELECT
tr.id
, t.qry
, tr.qry AS [sales]
FROM [test] t
LEFT JOIN #tmpResult tr
ON
t.id = tr.id
DROP TABLE #tmpResult
DROP TABLE #tmptest