Load fields from file using conditions

[Peony]

Hi all .

I have a table from which I need to load a fields. For example table |I have like this one:.

Num	A	B	C	F1	F2	FN
1	22	27	24	u
2	22	27	24		u	u
3	22	23	25			u

From this tableI need to Load field "Num", all fields starting with F and A or B or C.

Also I have an internal parameter vParam that may be equal  "A"  or "B" or "Null()".  In case if vParam  = A, than I should load field "Num", field "A" field (and not B or C) and all fields starting with F,  if vParam = B, then "Num", field B,all fields starting with F .  And if vParam  = Null() then loading "Num",  C, all fields starting with F .

Please, help me to understood how I may do Load from file with conditions I've described?

P.S.

If  vParam = A resulted  table should be like 

Num	A	F1	F2	FN
1	22	u
2	22		u	u
3	22			u

If  vParam = B resulted  table should be like

Num	B	F1	F2	FN
1	27	u
2	27		u	u
3	23			u

If  vParam = C resulted  table should be like

Num	C	F1	F2	FN
1	24	u
2	24		u	u
3	25			u

[avkeep01]

Hi @Peony , 

It isn't really clear what you want to do. But I think I can help you a bit further by directing you to a crosstable load. 

CROSSTABLE (Character,Number) LOAD * INLINE [
Num, A, B, C, F1, F2, FN
1, 22, 27, 24, u, , ,
2, 22, 27, 24, , u, u,
3, 22, 23, 25, , , u,
];

In that case the result will be like this. And that should make it more easy for you to make your selections. 

Num	Character	Number
1	F2
1	FN
2	F1
3	F1
3	F2
1	F1	u
2	F2	u
2	FN	u
3	FN	u
1	A	22
2	A	22
3	A	22
3	B	23
1	C	24
2	C	24
3	C	25
1	B	27
2	B	27

[Peony]

Hi @avkeep01 . Thank you for trying to help me. 
Unfortunately, your solution is not the result I need. I added some changes to the my post. Hopefully now it’s clearer what I'm looking for as a result.

[avkeep01 · Accepted solution]

Hi @Peony , 

Thanks for the update question. I think I've got your answer. 

// Create table with paramater values to loop over
ParamTable:
LOAD * INLINE [
ParamField
A
B
C
];

// Set basetable
BaseTable:
LOAD * INLINE [
Num, A, B, C, F1, F2, FN
1, 22, 27, 24, u, , ,
2, 22, 27, 24, , u, u,
3, 22, 23, 25, , , u,
];

// Set loop
FOR i = 0 TO NUM(NOOFROWS('ParamTable')-1);

// Set variable with paramater value
LET vParam = PEEK('ParamField',$(i),'ParamTable');


Table_A:
LOAD
Num,
'$(vParam)' AS ParamValue, // Get the paramater value (A, B or C) to see which field is fetched
$(vParam) AS ParamResult, // Get the field value from field A, B, or C
F1,
F2,
FN
RESIDENT BaseTable;

NEXT i;

DROP TABLE BaseTable,ParamTable;

This results in the following table.

Num	ParamResult	ParamValue	F1	F2	FN
1	22	A	u
3	22	A			u
2	22	A		u	u
1	27	B	u
3	23	B			u
2	27	B		u	u
1	24	C	u
3	25	C			u
2	24	C		u	u

[Peony]

@avkeep01  Yes, you got may idea correct! Thank you for help!