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How to sum values from a database column in AnyLogic?

as a newbie I want to sum the values of a column pv from a database table evm in my model and store it in a variable. I have tried the SQL code SELECT SUM(pv) FROM evm; but that doesn't seem to work.I would be grateful if you lend me an aid regarding how to pull this one.

You can always write a native query and get the response in the resultset to populate the field of your pojo. Once you have the POJO/DTO created as the list of result set perform your sum on the field by Iterating the list.

You do just use the SQL you have suggested. (The database in an AnyLogic model is a standard HSQLDB database which supports this SQL syntax.)
The simplest way to execute it is to use AnyLogic's in-built functions for such queries (as would be produced by the Insert Database Query wizard), so
mySumVariable = selectFirstValue("SELECT SUM(pv) FROM evm;");
You didn't say what errors you had; obviously the table and column has to exist (and the column you're summing needs to be numeric, though NULLs are OK), as does the variable you're assigning the sum to.
If you wanted to do this in a way which more easily fits one of the standard query 'forms' suggested by the wizard (i.e., not having to know particular SQL syntax) you could just adapt the "Iterate over returned rows and do something" code to 'explicitly' sum the columns; e.g., (using the Query DSL format this time):
List<Tuple> rows = selectFrom(evm).list();
for (Tuple row : rows) {
mySumVariable += row.get(evm.pv);
}

Database ResultSet get String/Integer with SELECT

I need to know what the number X needs to be in order to receive the data properly.
Example code :
Statement sta = (connection object).createStatement();
sta.executeQuery("SELECT 'points' FROM TABLEX WHERE 'player'='" + player_name + "'").getString(X); ///HERE

Either 1, or "points" will work.
1 is the index of the column as specified in the select statement. The indexing starts from 1 and increments from there.
Otherwise the name of the column may be used, in this case "points". That method may cause a bit more meta data to get loaded and so performance can vary.

As the javadoc says :
getString(int columnIndex)
Retrieves the value of the designated column in the current row of this ResultSet object as a String in the Java programming language. and
getString(String columnLabel)
Retrieves the value of the designated column in the current row of this ResultSet object as a String in the Java programming language.
So this is not going to work. It will give you :
java.sql.SQLException: Before start of result set
First of all you need to iterate through the Resultset obtained using next() then you can retrieve the specific values by either pass 1 which is the column index in this case or points which is the columnName of your table and based on the where clause it shall give you different values of the column points

X is the column number(index) in the table.
It is needed to fetch the data from table.
You also can use column name instead of column index like this -
getString(ColumnName);

How to determine if a table contains a value in SQL?

I feel like I'm missing something very obvious here, but it seems that the only way to go about doing this is to get the value, and then see if it returns a null (empty) value, which I would rather not do.
Is there an equivalent to List.contains(Object o) in SQL? Or perhaps the JDBC has something of that nature? If so, what is it?
I am using Microsoft Access 2013.
Unfortunately I don't have any useful code to show, but here is the gist of what I am trying to do. It isn't anything unique at all. I want to have a method (Java) that returns the values of a user that are stored in the database. If the user has not previously been added to the database, the user should be added, and the default values of the user should be set. Then those newly created values will be returned. If a player has already been added to the database (with the username as the primary key), I don't want to overwrite the data that is already there.
I would also advise against using MS Access for this purpose, but if you are familiar with MS Office applications, the familiar UI/UX structure might help you get your footing and require less time to learn other database environments. However, MS Access tends to be quite limited, and I would advise considering alternative options if available.

The only way to see if an SQL table contains a row with some condition on a column is to actually make an SQL query. I don't see why you wouldn't do that. Just make sure that you have an index on the column that you will be constraining the results on. Also for better speed use count to prevent from retrieving all the data from the rows.
SELECT count(*) FROM foos WHERE bar = 'baz'
Assuming you have an index on the bar column this query should be pretty fast and all you have to do is check whether it returns > 0. If it does then you have rows matching your criteria.

You can use "IF EXISTS" which returns a boolean value of 1 or 0.
select
if(
exists( select * from date1 where current_date()>now() ),
'today > now',
'today is not > now'
) as 'today > now ?' ;
+--------------------+
| today > now? |
+--------------------+
| today is not > now |
+--------------------+
1 row in set (0.00 sec)
Another Example:
SELECT IF(
EXISTS( SELECT col from tbl where id='n' ),
colX, colY
) AS 'result'
FROM TBL;

I'm also new to sql and I'm using Oracle.
In Oracle, suppose we have: TYPE: value.
We can use:
where value not in (select TYPE from table)
to make sure value not exist in the column TYPE of the table.
Don't know if it helps.

You can simply use Query with condition.
For example if you have to check records with particular coloumn, you can use where condition
select * from table where column1 = 'checkvalue'
You can use count property to check the no. of records existing with your specified conditon
select count(*) from table where column1 = 'checkvalue'

I have created the following method, which to my knowledge works perfectly. (Using the java.sql package)
public static containsUser(String username)
{
//connection is the Connection object used to connect to my Access database.
Statement statement = this.connection.createStatement();
//"Users" is the name of the table, "Username" is the primary key.
String sql = "SELECT * FROM Users WHERE Username = '" + username + "'";
Result result = statement.executeQuery(sql);
//There is no need for a loop because the primary key is unique.
return result.next();
}
It's an extremely simple and extremely basic method, but hopefully it might help someone in the future.
If there is anything wrong with it, please let me know. I don't want anyone learning from or using poorly written code.
IMPORTANT EDIT: It is now over half a decade after I wrote the above content (both question and answer), and I now advise against the solution I illustrated above.
While it does work, it prioritizes a "Java-mindset-friendly" approach to SQL. In short, it is typically a bad idea to migrate paradigms and mindsets of one language to another, as it is inevitable that you will eventually find yourself trying to fit a square peg into a round hole. The only way to make that work is to shave the corners off the square. The peg will then of course fit, but as you can imagine, starting with a circle peg in the first place would have been the better, cleaner, and less messy solution.
Instead, refer to the above upvoted answers for a more realistic, enterprise-friendly solution to this problem, especially as I imagine the people reading this are likely in a similar situation as I was when I originally wrote this.

Getting last record from mysql

I am using mysql and facing some problem. I want to retrieve last row that is inserted.
<< Below are details >>
Below is how I created table.
create table maxID (myID varchar(4))
I inserted four values in it as below
insert into maxID values ('A001')
insert into maxID values ('A002')
insert into maxID values ('A004')
insert into maxID values ('A003')
When I execute select myID, last_insert_id() as NewID from maxID, I get output as below
myId NewID
A001 0
A002 0
A004 0
A003 0
When I tried below code,
select myId, last_insert_id() as NewID, #rowid:=#rowid+1 as myrow from maxID, (SELECT #rowid:=0) as init
I get output as below.
myId NewID rowid
A001 0 1
A002 0 2
A004 0 3
A003 0 4
However when I use code select myId, last_insert_id() as NewID, #rowid:=#rowid+1 as myrow from maxID, (SELECT #rowid:=0) as init where #rowid = 4, I get error as Uknown column 'myrow' in where clause
When I use where #rowid=4, I don't get any data in tables.
Link to play with data
Note: Here I am using 4 just to get desired output. Later I can get this from a query (select max(rowid) from maxID)
Please suggest me what need to do if I want to see only last record i.e. A003.
Thanks for your time.
Update:
I already have millions of data in my table so I can't add new column in it as suggested below.

Almost done.
You succeed in getting the insert order.
So:
select myId, #rowid:=#rowid+1 as myrow from maxID, (SELECT #rowid:=0) as init ORDER BY myrow desc LIMIT 1;
In my console I get the following:
mysql> select myId, #rowid:=#rowid+1 as myrow from maxID, (SELECT #rowid:=0) as
init ORDER BY myrow desc LIMIT 1;
+------+-------+
| myId | myrow |
+------+-------+
| A003 | 4 |
+------+-------+
1 row in set (0.00 sec)
Demo
UPDATE
Yak is right. My solution is not deterministic. Maybe it works for small amount of records. I found tons of post abount unreliability of default sorting of a SELECT statement (here for example).
Next steps:
Under which conditions the default SELECT sorting matches the insertion order?
Is it possible to obtain the last inserted record in a table without an incremental id or an insertion timestamp?
I know it's not an answer, but stating the problem limit the problem.

It seems that a SELECT is not guaranteed to return rows in any specific order (without using an ORDER BY clause, of course).
As per the SQL-92 standard (p. 373):
If an < order by clause > is not specified, then the table specified by the < cursor specification > is T and the ordering of rows in T is implementation-dependent.
Okay, MySQL is not fully SQL-92-compliant, but this is a serious hint.
Laurynas Biveinis (apparently affiliated with Percona) also states:
The order of the rows in the absence of ORDER BY clause (...) could be different due to the moon phase and that is OK.
The MySQL manual says about InnoDB:
InnoDB always orders table rows according to [a PRIMARY KEY or NOT NULL UNIQUE index] if one is present.
As far as I am concerned, I assume MySQL could also reorder rows after an OPTIMIZE TABLE or even reuse empty spaces after many deletes and inserts (I have tried to find an example of this, and have failed so far).
Given your table structure, the bottomline is, unfortunately, that so many factors could have altered the order of the rows; I see no solution to reliably determine the order they were inserted. Unless you kept all binary logs since you created the table, of course ;)
Nevertheless, you may still want to add a sequence column to your table. Existing rows would be assigned a possibly inaccurate sequence number, but at least future rows will be correctly sequenced.
ALTER TABLE maxID ADD sequence INT DEFAULT NULL;
ALTER TABLE maxID ADD INDEX(sequence);
ALTER TABLE maxID MODIFY sequence INT AUTO_INCREMENT;
http://sqlfiddle.com/#!2/63a8d/1

From your insert script, A004 is not the last inserted record. It's the third one. If you want to get the last record in alphabetical order (which A004 is), you must use
select myID from maxID order by myID desc limit 1
If you want the last inserted row, why don't you just use add an autoincrement column to your table? That's the point of those kinds of columns. The autoincrement column doesn't have to be the PK (it should be, but doesn't have to if you don't have the choice).

As mentioned in the MySQL help for last_insert_id, you can only use it with **auto-increment columns. This means that you cannot make MySQL find the most recently inserted row for you, unless you know something about the order of the IDs. If they are sorted like your example suggests, then you can use
SELECT *
FROM maxID
WHERE myId = max(myId)
But I suggest adding an auto-increment column to the table and then use = last_insert_id() in your WHERE clause. See also this page for information on how to obtain the last ID.

last_insert_id does not work because it only returns the last value generated by an auto-increment field. However I think that solution may be on the right track. I would suggest adding another column that is a auto-increment integer. You can then insert data and to retrieve the row you just inserted select the last_insert_id(). To retrieve the most recent row (inserted by any process) select the max number for the new column, or sort by it desc.
If you want to use the varchar column you can do an alphabetic sort, but that does not guarantee it will be the last row you inserted row or even the most recently inserted row.
The one other solution I can think of which may do what you need is to create a stored procedure which creates the row, inserts it into the table, and then returns it to you.
Your usage of #rowid is simply counting the order rows are returned to you. There is no guarantee that they are returned to you in the order of oldest to newest. There are a variety of things that can affect the order in which rows are stored.

Please use the following query.
Select * from maxID order by myId desc limit 1,1;

Getting Number of Rows in a Group By Query with Microsoft Access

I have basically the same problem outlined in this question, however I am using Microsoft Access as a database instead of MySQL. The result of which is that SQL_CALC_FOUND_ROWS doesn't seem to be available to me. Believe me, I want to switch, but for the moment it is out of the question.
I have a query that aggregates a number of rows, essentially looking for repeat rows based on certain keys, using a group by. It looks something like this:
Select key1, key2, key3, Count(id)
from table
group by key1, key2, key3
having Count(id) > 1
I need to determine the number of rows (or groupings) that query will return.
The database is being accessed through Java, so in theory I could simply run the query, and cycle through it twice, but I was hoping for something faster and preferably SQL based. Any ideas?

MS Access's record count should give you what you need, or am I missing something?
If you need distinct values from keys, try this
SELECT COUNT(*) AS Expr2
FROM (
SELECT DISTINCT [key1] & "-" & [key2] & "-" & [key3] AS Expr1
FROM Table1
) AS SUB;

When you create the Statement object, you can declare it to be scrollable. Then the first thing you do is scroll to the end and get the record number. As you're looking at the last record, this will be the number of records in the result set. Then scroll back to the beginning and process normally. Something like:
Statement st=connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rs=st.executeQuery(myQueryString);
boolean any=rs.last();
int count = any ? count=getRow() : 0;
... do whatever with the record count ...
rs.first();
while (rs.next())
{
... whatever processing you want to do ...
}
rs.close();
... etc ...
I have no idea what the performance implications of doing this with MS Access will be, whether it can jump directly to the end of the result set or if it will have to sequentially read all the records. Still, it should be faster than executing the query twice.