Select table and column dynamically based on other table rows - sql

Question

I have following table and values,
Tb_name column_name1 column_name2
Citator_KTLO_CC Date_Created Date_Modified
Citator_KTLO_QA Date_Created Date_Modified
I want to select dynamically column from table, so the result is like this:
Select Date_Created,Date_Modified from Citator_KTLO_CC
and in next loop it will select for second row, like
Select Date_Created,Date_Modified from Citator_KTLO_QA
How can i do this by using dynamic sql ?
any example are appreciated.

Answer 1

here is an example of how to do this.
Since you dont post many info I just assume that the table containing all the tablenames is called 'tables'
Also this will only work if all tables have the same column types.
-- create a test table you dont need this
create table tables (tb_name varchar(100) primary key, field1 varchar(100), field2 varchar(100))
-- fill my test table you dont need this
insert into tables values ('table1', 'field1', 'field2')
insert into tables values ('table2', 'foo1', 'foo2')
insert into tables values ('table3', 'test1', 'test2')
-- this is the actual code you need, replace the names with your real names
declare #sql varchar(max) = ''
declare #tb_name varchar(100) = ''
declare #field1 varchar(100) = ''
declare #field2 varchar(100) = ''
declare myCursor cursor for
select tb_name, field1, field2 from tables -- dont know how your table is called
open myCursor
fetch next from myCursor into #tb_name, #field1, #field2
while ##FETCH_STATUS = 0
begin
set #sql = #sql + ' select ' + #field1 + ', ' + #field2 + ' from ' + #tb_name + ' union all '
fetch next from myCursor into #tb_name, #field1, #field2
end
close myCursor
deallocate myCursor
select #sql = left(#sql, len(#sql) - 10)
exec (#sql)
EDIT:
using a where clause is possible but things will get more complicated
declare #something date = getdate()
set #sql = #sql + ' select ' + #field1 + ', ' + #field2 + ' from ' + #tb_name + ' where ' + #field1 + ' = ' + #something + ' union all '
You can use the example above to build what you need just play with it.
EDIT:
using a where clause with a date format
declare #something date = getdate()
set #sql = #sql + ' select ' + #field1 + ', ' + #field2 + ' from ' + #tb_name + ' where ' + #field1 + ' = ''' + CONVERT(varchar(8), #something, 112) + ''' union all '

Answer 2

DECLARE #SQL VARCHAR(1000);
SET #SQL = '
SELECT *
FROM Citator_KTLO_CC
UNION ALL
SELECT *
FROM Citator_KTLO_QA;'
EXEC (#SQL);

Answer 3

How about something like this. If you've more than two cols, you can use dynamic sql to generate a list of cols to then generate more dynamic sql instead of hard coding.
DROP TABLE #Test
CREATE TABLE #Test
(Tb_name NVARCHAR(15),
column_name1 NVARCHAR(12),
column_name2 NVARCHAR(13));
INSERT INTO #Test VALUES
('Citator_KTLO_CC','Date_Created','Date_Modified'),
('Citator_KTLO_QA','Date_Created','Date_Modified');
DECLARE #SQL NVARCHAR(MAX)
SET #SQL = (SELECT STUFF((SELECT ' UNION ALL SELECT ' + Cols + ' FROM '+TbL
FROM (SELECT QUOTENAME(Tb_name) TBL,
QUOTENAME(column_name1) + ', '+
QUOTENAME(column_name2) Cols
FROM #Test) Blah
FOR XML PATH('')),1,10,''))
PRINT #SQL
EXEC sys.sp_executesql #SQL

Answer 4

Try this..
For selecting one row if you are running in aloop
DECLARE #sql NVARCHAR(4000)
SELECT #sql = ' select ' + column_name_1 + ',' + column_name2 + ' from ' + Tb_name
FROM < yourtable >
EXEC (#sql)
OR
DECLARE #sql NVARCHAR(4000)
SELECT #sql = 'union all select ' + column_name_1 + ',' + column_name2 + ' from ' + Tb_name
FROM < yourtable >
SET #sql =stuff(#sql,1,10,'')
EXEC (#sql)

Answer 5

DECLARE #ColumnList1 VARCHAR(MAX) = '''''';
DECLARE #ColumnList2 VARCHAR(MAX) = '''''';
DECLARE #ColumnNameFromTable1 VARCHAR(50);
DECLARE #ColumnNameFromTable2 VARCHAR(50);
DECLARE MyCursor1 CURSOR
FOR
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'Citator_KTLO_CC'
ORDER BY ORDINAL_POSITION
DECLARE MyCursor2 CURSOR
FOR
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'Citator_KTLO_QA'
ORDER BY ORDINAL_POSITION
OPEN MyCursor1
OPEN MyCursor2
FETCH NEXT FROM MyCursor1 INTO #ColumnNameFromTable1;
WHILE ##FETCH_STATUS = 0
BEGIN
FETCH NEXT FROM MyCursor2 INTO #ColumnNameFromTable2;
SET #ColumnList1 = #ColumnList1 + ',' + #ColumnNameFromTable1
SET #ColumnList2 = #ColumnList2 + ',' + #ColumnNameFromTable2
FETCH NEXT FROM MyCursor1 INTO #ColumnNameFromTable1;
END
CLOSE MyCursor1;
DEALLOCATE MyCursor1;
CLOSE MyCursor2;
DEALLOCATE MyCursor2;
EXEC ('SELECT ' + #ColumnList1 + ' FROM Citator_KTLO_CC UNION ALL SELECT ' +
#ColumnList2 + ' FROM Citator_KTLO_QA ')