Hello colleagues,

I have a similar problem. Connection and data transfer from PLC to SQL database works perfectly, except for string data which have different length.

For example,

In the PLC data block: the tag is defined as String[16]

In the SQL database: same tag is defined as nvarchar(50)

I guess that data transfer in this case doesn't work because of different length. But there is no possibility to change string length in the tag definition neither on PLC nor in SQL database.

Any suggestions? 

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Split from TIA Portal and SQL database.

Hello mrsaleksandra,

currently I can't provide a solution to your problem, but maybe a thought to narrow down the problem.

You said, that the you think the problem may be the different string length in PLC and Database.
I checked, how "nvarchar(x)" is defined (at https://docs.microsoft.com/de-de/sql/t-sql/data-types/nchar-and-nvarchar-transact-sql?view=sql-server-2017) and it is said, "x" is the maximal amout of characters which can be saved. But this is just a max, it should be possible to save lesser characters, as far is I understand this.

So, to conclude, the different string length should not be the problem.

But if it unexpectedly is the problem though, couldn't you set up a HMI tag with fitting string length, have you tried this?
Than you would read from PLC, write it into the HMI tag, than write the HMI tag to the SQL database.

Greetings,

Nzett11

Which WinCC type do you use, basic, comfort, adv, prof?

Hello Nzett11,

I am using WinCC 7.3.. I read AS symbols from PLC, so if I define a tag as String, in the WinCC it will be defined automatically as "Text tag 8-bit character set". On the other hand, if I define a tag as WString, it will be defined as "Text tag 16-bit character set". But...

Although it is defined as nvarchar(50) in the database, client never uses more than 16 characters.. Nevertheless, I have even been trying to change the length of String on the PLC side (in a test project) to see in what cases it does send values from WinCC, and in which cases it does not. The conclusion is the following:

*** In SQL database defined as nvarchar(50)

*** In WinCC defined as 8-bit or 16-bit character set (I have tried both)

*** In PLC datablock defined as:

1. Firstly as String[16] - didn't work
2. Then as String[150] - didn't work
3. Then as WString[50] - didn't work
4. Then as WString[150] - didn't work
5. Then as String (which is 255 bytes by default) -> only in this case the string is written from WinCC to PLC
6. I came up with an idea to define Array[1 .. 16] of Char and send character by character in a loop -> this also works

But I would prefer to keep the String structure, and not to move on the array of chars, because I would have to make a lot of changes in a project. I am just annoyed with the fact  that I can't figure out why every other data type transfer works, and Strings don't...... 

 Helll mrsaleksandra,

mrsaleksandra

[...]

5. Then as String (which is 255 bytes by default) -> only in this case the string is written from WinCC to PLC

[...]

what about the following, does that work?

- Define String[16]-tag in PLC and create a tag in WinCC that links to the PLC-tag.

- Then read the string from database and write only the left 16 characters to the WinCC-tag.

Regards,

Frink