How to fix dynamic sql query syntax error that shown in below in synapse?

Question

IF OBJECT_ID('temp..#temp') IS NOT NULL
BEGIN
    DROP TABLE #temp
END
GO

CREATE TABLE #temp
(
    [CxID] int,
    [CompanyID] int,
    [Category] int -- this category column is created by ROW_NUMBER function over partition by [CxID] order by [CxID] and [CompanyID]
)

INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('1', '101', '1');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('1', '102', '2');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('1', '103', '3');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('2', '201', '1');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('3', '301', '1');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('4', '401', '1');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('5', '501', '1');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('5', '502', '2');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('5', '503', '3');
INSERT INTO #temp ([CxID], [CompanyID], [Number]) VALUES ('5', '504', '4');
DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX);

SET @cols = (SELECT STRING_AGG(category,',') FROM (SELECT DISTINCT category FROM #temp WHERE category IS NOT NULL)t);

set @query = 'SELECT date, ' + @cols + ' from 
            (
                select CxID
                    , CompanyID
                    , category
                from #temp
           ) x
            pivot 
            (
                 max(CompanyID)
                for category in (' + @cols + ')
            ) p ';

execute(@query);

Error Message: Parse error at line: 11, column: 34: Incorrect syntax near '1'.

Question: We don't know the maximum number of CompanyID that customer can have in the historical data, and want to output like following:

CxID	CompanyID1	CompanyID2	CompanyID3	...	CompanyIDx
1	101	102	103	...	(NULL)
2	201	(NULL)	(NULL)	...	(NULL)
3	301	(NULL)	(NULL)	...	(NULL)
4	401	(NULL)	(NULL)	...	(NULL)
5	501	502	503	...	...

Answer 1

I think you should try to avoid numbers as columns because pivot is bad with them.

But if you want then you have to change sql so it becomes like this:

SELECT [1],[2],[3],[4] from 

instead of

SELECT 1,2,3,4 from