How do I stop blank output from FOR XML PATH in SQL server for dynamic sql?

Question

I was trying to generate a script for data vault, below is the dynamic sql that would generate tables for many to many relations:

DECLARE @LOAD_DATE_RS VARCHAR(100)
SET @LOAD_DATE_RS = 'LOAD_DATETIME DATETIME NOT NULL,' + CHAR(10) 
                    + 'RECORD_SOURCE VARCHAR(100) NOT NULL,'+CHAR(10)
DECLARE @CREATE_LINK_M_N_RELN VARCHAR(MAX)                  
SET  @CREATE_LINK_M_N_RELN = (SELECT    
                                'CREATE TABLE LINK_'+ REPLACE(HL.TABLENAME, ' ', '_') + CHAR(10)
                                + '( '
                                    + ( SELECT  
                                            DISTINCT FPR.PK_TABLE + '_ID  INT NOT NULL,'+ CHAR(10)
                                        FROM    
                                            FK_PK_REF FPR
                                        WHERE   
                                            FK_Table IN (   SELECT 
                                                                HL2.TABLENAME 
                                                            FROM 
                                                                HUB_OR_LINK HL2 WHERE HL2.HUBORLINK= 'LINK'
                                                                AND HL2.TABLENAME = HL.TABLENAME)
                                        FOR XML PATH (''))
                            --GET PRIMARY KEYS --HAS SOME PROBLEMS
                            +(  SELECT  
                                    DISTINCT C.COLUMN_NAME 
                                    + ' '+ C.DATA_TYPE      
                                    +   CASE WHEN C.DATA_TYPE IN('CHAR','VARCHAR','NVARCHAR') THEN 
                                            '('+CAST(C.CHARACTER_MAXIMUM_LENGTH AS VARCHAR(100))+')'
                                        ELSE 
                                            ' ' 
                                        END 
                                    +','+ CHAR(10)
                                FROM    
                                     INFORMATION_SCHEMA.COLUMNS C 

                                WHERE   
                                    C.TABLE_NAME = HL.TABLENAME
                                AND C.COLUMN_NAME IN (SELECT CCU2.COLUMN_NAME FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE CCU2
                                                        INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON 
                                                        CCU2.CONSTRAINT_CATALOG = TC.CONSTRAINT_CATALOG
                                                        AND CCU2.CONSTRAINT_SCHEMA = TC.CONSTRAINT_SCHEMA
                                                        AND CCU2.CONSTRAINT_NAME = TC.CONSTRAINT_NAME
                                                        WHERE TC.TABLE_NAME = HL.TABLENAME
                                                        AND TC.CONSTRAINT_TYPE = 'PRIMARY KEY')
                                AND C.COLUMN_NAME NOT IN (SELECT 
                                                                C.COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS C
                                                                INNER JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE CCU3
                                                                ON C.TABLE_CATALOG = CCU3.TABLE_CATALOG
                                                                AND C.TABLE_SCHEMA = CCU3.TABLE_SCHEMA 
                                                                AND C.TABLE_NAME = CCU3.TABLE_NAME
                                                                AND C.COLUMN_NAME =CCU3.COLUMN_NAME

                                                                INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON 
                                                                CCU3.CONSTRAINT_CATALOG = TC.CONSTRAINT_CATALOG
                                                                AND CCU3.CONSTRAINT_SCHEMA = TC.CONSTRAINT_SCHEMA
                                                                AND CCU3.CONSTRAINT_NAME = TC.CONSTRAINT_NAME
                                                                AND TC.CONSTRAINT_TYPE = 'PRIMARY KEY'
                                                            WHERE   
                                                                C.TABLE_NAME 
                                                            IN (SELECT 
                                                                    HL4.TABLENAME FROM HUB_OR_LINK HL4 
                                                                WHERE 
                                                                    HL4.HUBORLINK = 'HUB'

                                                                ) --GET ALL HUBS
                                                            )


                                FOR XML PATH ('')
                            )
                            +  @LOAD_DATE_RS
                            + 'CONSTRAINT PK_LINK_' +REPLACE(HL.TABLENAME, ' ', '_') + '  PRIMARY KEY (' 
                            +(  SELECT  
                                    DISTINCT PK_TABLE+'_ID,'
                                FROM    
                                    FK_PK_REF
                                WHERE   
                                    FK_Table NOT IN (SELECT DISTINCT PK_Table FROM FK_PK_REF)
                                    AND FK_TABLE = HL.TABLENAME
                                FOR XML PATH('')
                             )

                            + '))'+CHAR(10)+CHAR(10)
                    FROM    HUB_OR_LINK HL INNER JOIN INFORMATION_SCHEMA.TABLES T 
                    ON
                            T.TABLE_NAME = HL.TABLENAME
                    WHERE   HL.HUBORLINK = 'LINK'
                    FOR XML PATH (''))

SELECT @CREATE_LINK_M_N_RELN = REPLACE(@CREATE_LINK_M_N_RELN,',))','))');
PRINT @CREATE_LINK_M_N_RELN

The part that is adding the primary keys of the source table to the definition from the comment --GET PRIMARY KEYS --HAS SOME PROBLEMS to @LOAD_DATE_RS. If that part returns a blank output (meaning there are no tables with extra primary keys) then the whole output is blank. How do I stop this? If that part is blank then still I need to get the other dynamic SQL built so that I can execute it to get the tables I want. Please Help

Answer 1

By "Blank" do you mean an empty string or Null? If it is null, You could wrap an IsNull() around that portion of the concatenation.

If you run the troubling section on it's own without For XML Path(''), does it return all of the expected values?