What's command to check if already exist a column in a free table

[pomodoro]

Hello,
What is the command to check if already exist a column in a free table ?
Thanks

 

[Mike Lewis]

You can use VARTYPE() for this. If it returns U, then the field is not present. Example:

[tt]SELECT Customer
IF VARTYPE(Cust_Name) = "U"
* Field Cust_Name does not exist
ENDIF
[/tt]

But be careful. If Cust_Name exists as a variable, then the function won't return U.

An alternative would be to use AFIELDS() to get the field names into an array:

[tt]AFIELDS(laFields, "customer")
IF ASCAN((laFields, "CUST_NAME", -1, -1, 1) = 0
* Field Cust_Name does not exist
ENDIF[/tt]

Mike


__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[Olaf Doschke]

Well, you can check VarType(Customer.Cust_Name). But even that might also be a property Cust_Name of an object Customer. Field existence can be determined with FIELD():

USE customer.dbf
IF EMPTY(FIELD("cust_name","customer"))
   * field cust_name doesn't exist in workarea customer
Endif

Bye, Olaf.

 

[Mike Lewis]

VarType(Customer.Cust_Name)

But if that test fails, you would get a "Variable not found" error.

Mike



__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[EzLogic]

I made a function that i use often, especially when doing updates to the tables.

? FieldExist('ARCust','CustNO') && Table ARCust, Field = 'custNo



FUNCTION FieldExist(tcTable,tcField)

	IF NOT USED(tcTable)
                use (tcTable) in 0 
	ENDIF

	llFound	= .F. && not found
	SELECT (tcTable)
	FOR gnCount = 1 TO FCOUNT( )  && Loop for number of fields
		IF UPPER(ALLTRIM(FIELD(gnCount))) == UPPER(ALLTRIM(tcField))  && Display each field
			llFound = .T. && found it
			EXIT
		ENDIF
	NEXT
	RETURN llFound
ENDFUNC

Ez Logic
Michigan

 

[Olaf Doschke]

You're ALMOST right Vartype(fdsjkhfsdkjh.fhjksdhfk) errors "Alias 'FDSJKHFSDKJH' is not found". Anyway, it will not have that problem if tha table is open. FIELD() too.

Bye, Olaf.

 

[Mike Lewis]

But if the alias is found, but the field is not, I think you will get "Variable not found".

So, if you want to know if your Customer table contains a field called Company, and if you do this:
[tt]
USE Customer
? VARTYPE(Customer.Company)[/tt]

then you will get C (or some other letter, but not U) if the test succeeds. But you will get the error message if the test fails.

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[Olaf Doschke]

I see, anyway, the final recommendation is FIELD(), not Varttype. I was just trying to avoid the problem of just testing Vartype(field) and getting a type that isn't a field but a variable type.

FIELD() always will look into fields, not variables. and Field("wrongfieldname") will not error, just be empty.

Bye, Olaf.

 

[Mike Lewis]

the final recommendation is FIELD()

I can't argue with that. It looks like the neatest solution.

Mike



__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads