need clarification on sql query written in . java file

hi  everyone i have query in my .java file these kind of queries basically we are using to fetch some records from db.
i want to understand these kind of queries written in many places.
is there any siter to understand such kind of queries?

here is the query:
String sql = "SELECT ticket FROM Destination ticket "
                              + " WHERE ticket.sendAttempts < :threshold AND "
                              + " ticket.currentStatus.distributionType = :distType AND (";
                  
                  for (int i = 0; i < statuses.size(); i++) {
                        sql += "ticket.currentStatus.ticketStatusType=:status" + i;
                        if (i != statuses.size() - 1)
                              sql += " OR ";
                  }
                  sql += ")";





can any one explain what this query will do and how can i learn such kind of queries
For me it is difficult to understand.
Thanks.
LVL 2
srikoteshAsked:
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Mahesh BhutkarConnect With a Mentor Commented:
It seems that you are using Hibernate HQL here.

This is complex hql example which contains conditional joins on currentStatus object.
Here currentStatus has association with Destination.

It returns ticket as object with conditions
1) ticket.sendAttempts < :threshold
2) ticket.currentStatus.distributionType = :distType
   Join with Destination & currentStatus and condition on distributionType
3) ticket.currentStatus.ticketStatusType=:status
   Join with Destination & currentStatus and condition on ticketStatusType

You can refer HQL for more clarification from, http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/queryhql.html
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smiliefaceConnect With a Mentor Commented:
The string you have there will construct a SQL query that will return a collection of rows stored in a table Destination.

The reference "tickets" is an alias to the destination.

The "for" section is constructing an list of ticket statuses which are to be included.

I don't recognise what is happening to the "ticket.currentStatus.distributionType" as a 3 part name for a column isn't a regular SQL construction.
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dpearsonConnect With a Mentor Commented:
More generally if you're looking to learn SQL, there are plenty of sites out there.

For example try this one:
http://www.sqlcourse.com

specifically this part deals with select statements:
http://www.sqlcourse.com/select.html

which is the kind of query you posted.

Hope that helps,

Doug
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tliottaConnect With a Mentor Commented:
Also, note that you're not actually asking about SQL nor even about a "query". What you're asking about is programming a loop, which is very different from SQL or a query. The loop is simply building a string named "sql" by adding characters to it each time through the loop.

It's only when the loop finishes and passes the sql variable to a query engine that a query gets involved.

The best way to learn what it's doing is to look at the sql String variable each time the loop runs. That might be done in a debug session, or by adding a statement in the loop to display or print the variable.

In order to explain a "query", we would need to see the final version of the statement that gets built (though it's pretty clear what's happening) and we'd have to know what query engine is used.

Tom
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srikoteshAuthor Commented:
thanks bonzermahesh.

hi tliotta , i am using db2,and one more thing is i want to practice such kind of queries can you suggest any advice, the above urlsi have seen so far is all are sql queries whatever i posted that  is some thing  different  from sql query that is not simple sql query.

if it is like that i can search in google then i can understand.
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Mahesh BhutkarConnect With a Mentor Commented:
Using Java programming you are creating here dynamic HQL query.
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srikoteshAuthor Commented:
Thanks for your valuble suggestions
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