return value from dpQuery function

[MassEffect]

Hello!
What value and type of value will I get if dpQuery couldn't find any record in WinCC OA's database?
In case of using timerange to make request for example.

[adaneau]

Hi,

You'll get an emtpy dyn_dyn_anytype.

BR
Alexandre

[MassEffect]

You'll get an emtpy dyn_dyn_anytype.

How can I check that?
Can I compare empty dyn_dyn_anytype's value with empty string like this:

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if("" == empty dyn_dyn_anytype' value) ...

[leoknipp]

A dpQuery which was executed without an error will always at least return the header information (1 line in the result table).
You can check with dynlen() if the result of the query contains more than 1 line.

Best Regards
Leopold Knipp
Senior Support Specialist

[MassEffect]

Does it exist any function that can define type of variable?
For example type of this (after dpQuery request) returnValue[2][2] ?
I recieve two lines ( returned with dynlen() ) and empty value that I get from returnValue[2][2].

[leoknipp]

If you do a dpQuery() you know which data (and datatype) is returned in which column of the result table.
Then you can define a variable of the same typ and assign the values from the result table by addressing it with [line][column].

Best Regards
Leopold Knipp
Senior Support Specialist

[MassEffect]

Thank you very much for answers, but how to understand the difference between the empty value and zero?
If I want to compare them result is TRUE for both of them.

If result varible is empty or equal zero:

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if(result == 0)

always returns TRUE

[adaneau]

Hi,

If you wanna know if your query result is empty or not just use:

Code: Select all

if(dynlen(res)>1)
  //not empty
else
 //empty

[leoknipp]

As written in my previous posting you have to know which datatype is saved in which column of the query result if you want to do a comparison.
If a string value is written to a column you can check if the string is emptry by comparing it to "". For numerical values you can do a value comparison.

Best Regards
Leopold Knipp
Senior Support Specialist