SQL pivot table1 into table2 without using dynamic SQL pivot or hardcode query - sql

Question

I have seen many questions and answers given about pivoting table with SQL, with dynamic SQL pivot or hard code query with CASE WHEN.
However is there any way I can pivot table without using those 2?
Table 1:
| col1 | col2 | col3 |
|--------|-------|--------|
| ABCD | 1 | XY123 |
| ABCD | 2 | RT789 |
| PQST | 3 | XY123 |
| PQST | 4 | RT789 |
Pivoting to
| col1 | ABCD | PQST |
|--------|-------|-------|
| XY123 | 1 | 3 |
| RT789 | 2 | 4 |
My idea was to retrieve the structure of the col with:
WITH
structure AS (
SELECT DISTINCT
col3 AS col1, col1 AS colName, col2 AS values
FROM table1 ori
)
and then extracting matched values of each cell with joins and storing them temporarily. At last JOIN again populating them in the output. However I am stuck after the above step. I can't use PIVOT and have to do this dynamically (i.e. can't use the method to hardcode each value with CASE WHEN)
How can I achieve this?

Answer 1

This is not as efficient (and not as easy to code) as a dynamic pivot. However, it is doable.
It does all need to be dynamic e.g., creating each SQL statement as a string and executing that.
The process involves
Determine the column names (store in a temporary table)
Creating the table with the first column only
Populating that first column
For each additional column name
Adding a column to the table (dynamically)
Populating that column with data
You haven't specified the database - I'll illustrate the following below using SQL Server/T-SQL.
The following are in this db<>fiddle so you can see what's going on.
CREATE TABLE #ColNames (ColNum int IDENTITY(1,1), ColName nvarchar(100), ColNametxt nvarchar(100));
INSERT INTO #ColNames (ColName, ColNametxt)
SELECT DISTINCT QUOTENAME(Col1), Col1
FROM table1;
This will populate the #ColNames table with the values 1, [ABCD], ABCD, 2, [PQST], PQST.
The next step is to create your output table - I'll call it #pvttable
CREATE TABLE #pvttable (col1 nvarchar(100) PRIMARY KEY);
INSERT INTO #pvttable (col1)
SELECT DISTINCT Col3
FROM table1;
This creates your table with 1 column (col1) with values XY123 and RT789).
The write your favorite loop (e.g., cursor, while loop). In each step
Get the next column name
Add the column to the table
Update that column with appropriate data
e.g., the following is an illustrative example with your data.
DECLARE #CustomSQL nvarchar(4000);
DECLARE #n int = 1;
DECLARE #ColName nvarchar(100);
DECLARE #ColNametxt nvarchar(100);
SELECT #ColName = ColName,
#ColNameTxt = ColNameTxt
FROM #ColNames
WHERE ColNum = #n;
WHILE #ColName IS NOT NULL
BEGIN
SET #CustomSQL = N'ALTER TABLE #pvttable ADD ' + #ColName + N' nvarchar(100);';
EXEC (#CustomSQL);
SET #CustomSQL =
N'UPDATE #pvttable SET ' + #Colname + N' = table1.col2'
+ N' FROM #pvttable INNER JOIN table1 ON #pvttable.col1 = table1.col3'
+ N' WHERE table1.col1 = N''' + #ColNametxt + N''';';
EXEC (#CustomSQL);
SET #n += 1;
SET #ColName = NULL;
SET #ColNametxt = NULL;
SELECT #ColName = ColName,
#ColNameTxt = ColNameTxt
FROM #ColNames
WHERE ColNum = #n;
END;
SELECT * FROM #pvttable;