Modes and Methods in Tag Query and SQL Query

Question

Hi,
Can someone explain me about the modes available in <b>TAG Query and SQL Query.</b>
TAG Query has modes such as <b>Current, CurrentWrite, GroupList, History, HistoryEvent, ModeList, Statistics and TagList</b>
SQL Query i still have doubt on <b>FixedQuery with output , Modelist and TableList</b>
I also need to know why methods are used?
Thanks in advance
Regards
Muzammil

Answer 1

I'll try to  explain to the best of my knowledge :
<u><b>TagQuery</b></u>
<b>Current</b> : Gives you the current value of the Tag you are reading.
<b>CurrentWrite</b> : Let you write a Value as the Current Value of the Tag.
<b>GroupList</b> : Generally Tags are grouped under different groups. Returns you the name of the Groups.
<b>From the xMII Help Document :</b>
<b>History</b> : History Mode returns interpolated data.  Interpolation can be accomplished by specifying either the # of rows desired or the retrieval resolution.  If the mode is "History" and a value is provided for the Resolution parameter (which is in seconds), the connector will retrieve evenly-spaced values starting at the beginning of the time interval, up to the maximum # of rows specified in the RowCount parameter.  If no value is provided for the Resolution parameter, the connector will return an evenly-spaced number of values based on the value of the RowCount parameter.
For example, if the time interval is 1 hour, Resolution is 15, and RowCount is 240, the connector will return evenly spaced values each 15 seconds, up to 240 values (which would span the entire hour).
If the time interval is 1 hour, Resolution is not provided or is set to zero, and RowCount is 120, the connector would return 120 evenly spaced values, at an effective interval of 30 seconds.
<b>HistoryEvent Mode</b> : The connector can provide historical values "as they were stored" the database.  This mode provides no interpolation of values.
<b>Statistics Mode</b> : When retrieving data for statistical calculations, the connector utilizes the same techniques as in the "HistoryEvent"  mode.  It is important to note that the first two returning columns in the HistoryEvent query must be the timestamp and the value, in that order.  The SAP xMII Statistical processor expects that order, or errors will occur.  This ensures precision of statistical measurements, particularly time-weighted average, by using the exact storage time and values from the historical database.  The SAP xMII system provides the statistical calculations.
<b>Modelist</b> : Basically returns the modes of the Query Available. The Data returned is same as the data in the Modes list in the Quert Template Editor.
<b>Taglist</b> : Returns all the Tags in the Datasource.
<u><b>SQL Query</b></u>
<b>Modelist</b> : Same as above.
<b>TableList</b> : List of all the tables in the database to which the connector connects.
Again from SAP xMII Help Documentation :
<b>FixedQueryWithOutput</b> : This mode is used to execute an Oracle stored procedure or function that returns a REF CURSOR as output.  The position of the REF CURSOR is marked by a "?" in the query.  For example:
<b>Create a table.</b>
<i>create table usage (id int, name varchar(50));
insert into usage (id, name) values (1, 'test1');
insert into usage (id, name) values (2, 'test2');
insert into usage (id, name) values (3, 'test3');
insert into usage (id, name) values (4, 'test4');
insert into usage (id, name) values (5, 'test5');
insert into usage (id, name) values (6, 'test6');
insert into usage (id, name) values (7, 'test7');
insert into usage (id, name) values (8, 'test8');</i>
<b>Define the stored procedure.</b>
<i>DROP PACKAGE foopkg;
CREATE PACKAGE foopkg IS
  TYPE cursortype is ref cursor;
  PROCEDURE test (mycursor in out cursortype);
END foopkg;
CREATE PACKAGE BODY foopkg IS
  PROCEDURE test (mycursor in out cursortype) AS
  BEGIN
     open mycursor for select * from usage;
  END;
END foopkg;
</i>
Define a query template for calling the stored procedure.  Enter the following in the FixedQuery tab:
<b>call foopkg.test(?)</b>
This template returns all rows from the Usage table.