Aliasing column names dynamically in SQL Server - sql

Question

Providing separate aliasing values to each column dynamically. The number of values in #column_name1 and #aliasing_val can change as per requirements, so please provide a solution that can work for any number of values in the #column_name1 and #aliasing_val.
Declare #table_name1 NVARCHAR(250) = 'table1',
#column_name1 NVARCHAR(250) = 't1col1,t1col2,t1col3',
#aliasing_val NVARCHAR(250) = 'c1,c2,c3',
#SQLString nvarchar(max),
#SQLString2 nvarchar(max)
If ((#table_name1 IS NOT NULL AND LEN(#table_name1) !=0)
AND (#column_name1 IS NOT NULL AND LEN(#column_name1) !=0))
BEGIN
set #SQLString2 = 'SELECT '
Select #SQLString2 = #SQLString2 +
QUOTENAME(split.a.value('.', 'VARCHAR(100)')) + ' As '+aliasing_val+',
'
FROM (SELECT Cast ('<M>' + Replace(#column_name1, ',', '</M><M>')+ '</M>' AS XML) AS Data) AS A
CROSS apply data.nodes ('/M') AS Split(a);
Set #SQLString2 = LEFT(#SQLString2, LEN(#SQLString2) - 3)
END
print #SQLString2
Current output:
SELECT [t1col1] As c1,c2,c3,
[t1col2] As c1,c2,c3,
[t1col3] As c1,c2,c3
Expected output
SELECT [t1col1] As c1,
[t1col2] As c2,
[t1col3] As c3

Answer 1

This should do the job. You need to separate the comma-separated elements of each string out one at a time. This script loops through the items and maintains a pointer to the next item in the list. Then at each loop it extracts the item and adds it to the SQL:
Declare #table_name1 NVARCHAR(250) = 'table1',
#column_name1 NVARCHAR(250) = 't1col1,t1col2,t1col3',
#aliasing_val NVARCHAR(250) = 'c1,c2,c3',
#SQLString nvarchar(max),
#SQLString2 nvarchar(MAX),
#count [int],
#pos int,
#pos2 [int],
#delimiter varchar(1);
SET #delimiter = ',';
SET #pos = CHARINDEX(#delimiter, #aliasing_val, 1)
SET #pos2 = CHARINDEX(#delimiter, #column_name1, 1)
SET #aliasing_val = LTRIM(RTRIM(#aliasing_val)) + #delimiter
SET #column_name1 = LTRIM(RTRIM(#column_name1)) + #delimiter
SET #count = 0
IF ((#table_name1 IS NOT NULL AND LEN(#table_name1) !=0) AND (#column_name1 IS NOT NULL AND LEN(#column_name1) !=0))
BEGIN
SET #SQLString2 = 'SELECT '
IF REPLACE(#aliasing_val, #delimiter, '') <> '' -- make sure there are actually any delimited items in the list
BEGIN
WHILE #pos > 0
BEGIN
IF #count > 0 SET #SQLString2 = #SQLString2 + ','
SET #SQLString2 = #SQLString2 + LTRIM(RTRIM(LEFT(#column_name1, #pos2 - 1))) + ' As ' + LTRIM(RTRIM(LEFT(#aliasing_val, #pos - 1)))
SET #aliasing_val = RIGHT(#aliasing_val, LEN(#aliasing_val) - #pos) -- remove the item we just extracted from the list
SET #column_name1 = RIGHT(#column_name1, LEN(#column_name1) - #pos2) -- remove the item we just extracted from the list
SET #pos = CHARINDEX(#delimiter, #aliasing_val, 1) -- reset the position to point to the next delimiter
SET #pos2 = CHARINDEX(#delimiter, #column_name1, 1) -- reset the position to point to the next delimiter
SET #count = #count + 1
END
END
END
SELECT #SQLString2

Answer 2

You are at the right approach. Only thing you need to do is make two separate select statement for #column_name and #aliasing_val and join it using ROW_NUMBER() function and you got what you expect - Try this
IF ((#table_name1 IS NOT NULL AND LEN(#table_name1) !=0) AND (#column_name1 IS NOT NULL AND LEN(#column_name1) !=0))
BEGIN
SET #SQLString2 = 'SELECT '
SELECT #SQLString2 += tab.ColName + ' As '+ res.AliasName +','
FROM
(
SELECT QUOTENAME(split.a.value('.', 'VARCHAR(100)')) AS ColName, ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS RowNum
FROM
(
SELECT Cast ('<M>' + Replace(#column_name1, ',', '</M><M>')+ '</M>' AS XML) AS Data
) AS A
CROSS apply data.nodes ('/M') AS Split(a)
) tab
INNER JOIN
(
Select AliasSplit.c.value('.', 'varchar(100)') AS AliasName, ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS RowNum
FROM
(
SELECT Cast ('<A>' + Replace(#aliasing_val, ',', '</A><A>')+ '</A>' AS XML) AS AliasData
) AS A
CROSS apply AliasData.nodes ('/A') AS AliasSplit(c)
) res
ON tab.RowNum = res.RowNum
Set #SQLString2 = LEFT(#SQLString2, LEN(#SQLString2) - 1)
END
PRINT #SQLString2
Output
SELECT [t1col1] As c1,[t1col2] As c2,[t1col3] As c3