Does ignite cache maintains String pool as it is done by JVM? For ex if I want to store the objects of following Employee class:
public Class Employee{
int empId,
String departmentName
}
Since multiple emp objects will have same departName, Will there be memory optimization done by ignite, So that there won't be muliple times memory allocation for the departmentName, having same value?
There is no such feature in Ignite out of the box, but you can implement something similar using a dictionary table.
For example instead of having a single table Employee (empId int, departmentName varchar) you can have two: Emplloyee (empId int, depId int) and Departments (depId int, depName varchar). So, repeating department names will be stored only once. The same approach can be applied for any values that can occur multiple times in the database.
Related
Select firstname as name, time as asof, salary as bal into temp employee
from people.person p
where p.id =1;
Need to create a temporary table employee by inserting values from already created table person which belongs to people database but getting error from keyword not found where expected
You'd then use CTAS (Create Table As Select), not an invalid INTO clause; it is used for different purposes.
create table temp_employee as
select firstname as name,
time as asof,
salary as bal
from people.person p
where p.id = 1;
Based on comment you posted, there are several options you might want to consider.
One is to create a permanent table (just like the above example shows). If you'll reuse it, then - in your procedure - first delete its contents (or truncate the table as it is way faster), and then re-populate it:
delete from temp_employee;
-- or truncate table temp_employee;
insert into temp_employee
select firstname, time, salary from people.person
where id = 1;
Another option is to create a true temporary table, e.g.
create global temporary table temp_employee
(name varchar2(30),
time date,
bal number
)
on commit preserve rows;
Whenever you need data in it, just insert it:
insert into temp_employee (name, time, bal)
select firstname as name,
time as asof,
salary as bal
from people.person p
where p.id = 1;
Doing so, its contents will be visible only to you (and nobody else), while table's contents will be kept during the transaction or session (it depends on how you created it - see the on commit preserve/delete rows clause).
What you should not do is to create the table, drop it, then create it again, and so on - in Oracle, we create table once and use it many times.
I have an SSIS Package that runs a query and inserts values into a different table. Each time the package runs, I want to create a unique RunID for the results of that run. Here are the columns from my table. I have tried this using the Execute SQL Task and setting up the User::RunID variable but, I believe I am doing something wrong. Can anyone provide step by step instructions on how to do this?
You need 2 tables for this.
create table runs(
runID int identity primary key,
runDateTime datetime default getdate()
)
create table runReturns(
runReturnsID int identity primary key,
runID int not null,
[the rest of the data set]
)
In ssis, start with an execute SQL.
Add this query...
insert into runs (runDateTime) values(?);
select SCOPE_IDENTITY()
Map the parameter (?) to Now();
Change the result set to single row and map the first column to a parameter called runID.
Now create a data flow.
Insert your query into a sql source.
Add a derived column and map a new column to runID.
Finally, add a destination to your table and map accordingly.
Adding a completely sql answer to compliment as an alternative since there are no transformations at all:
Same 2 tables:
create table runs(
runID int identity primary key,
runDateTime datetime default getdate()
)
create table runReturns(
runReturnsID int identity primary key,
runID int not null,
[the rest of the data set]
)
Create a Job.
Add a step and base it on SQL.
declare #runID int;
insert into runs(runDateTime) values(getdate());
select #runID = scope_idenity();
insert into runReturns(
runID, [rest of your columns])
select #runID
, [rest of your columns]
from [rest of your query]
An approach that might solve the issue, is the system scoped variable ServerExecutionID By default, System scoped variables are hidden in the Variables menu but you can expose them by clicking the Grid options button (rightmost of the 5).
If you reference that variable using the appropriate placeholder (? for OLE/ODBC or a named parameter for ADO) and map to the variable, then every server execution will have a monotonically increasing number associated to it. Runs from Visual Studio or outside of the SSISDB, will always have a value of 0 associated to them but given that this is only encountered during development, this might address the issue.
Sample query based on the newer picture
INSERT INTO dbo.RunMapTable
SELECT ? AS RunID
, D.Name
FROM
(
VALUES ('A')
, ('B')
, ('C')
, ('D')
)D([name];
Parameter Mapping
0 -> System::ServerExecutionID
As an added bonus, you can then tie your custom logging back to the native logging in the SSISDB.
I'm trying to create a table in Oracle as follows:
create table person (
person_id number(5) generated always as identity
minvalue 1
maxvalue 99999
increment by 1 start with 1
cycle
cache 10,
firstname varchar(10),
lastname varchar(10));
This works all fine, but when I try something like this:
insert into person
values ('firstname', 'lastname');
I'm getting an error. When I try putting in a number where the ID should be, I get a different error.
I'm confused because I originally thought that formatting the person_id in this way automatically generated unique ID values, so that I wouldn't be able to put them in.
I'm also a bit confused on how this all fits into JDBC. If I'm working with Java and I insert a tuple into such a table, how am I able to get the generated ID into my Java program? I can't search by first and last name, because there could be two people with the same name.
You need to list the columns for an insert:
insert into person(firstname, lastname)
values ('firstname', 'lastname');
The fact that the column is generated doesn't affect the syntax of the insert. So, with no columns, the insert is the same as:
insert into person(person_id, firstname, lastname)
values ('firstname', 'lastname');
And with two values and three columns, you are getting an error.
I am working on a database, using Sql Server 2012. In our data model we have a type of User, with basic login information, name, address, etc, etc. Some of these users will be Technicians, who have all the same properties as a User, but some other properties like Route, Ship To Location, etc.
My question is, in designing a database, how does one simulate this situation. I have thought of 2 options.
Have a foreign key in the Technician table to the PK of the User database to link them up. My worry with this one is how will I know if a user is a technician, I would have to run a query on the technicians table each time a user logs in.
Have a field in User table link up with the PK of the Technician database, and if this field is null, or -1 or whatever I know this user is not a technician. I dont see any immediate problems with this one, but I am no expert at database design.
Do either of these have an advantage, and if so, why? Currently I have 2 different tables with two completely different id's, and they are not linked in any way, which I am now facing problems because of.
lets say you have 3 different sub class type of Class user. you can have a column in User table to identify the subclass Type. for example UserTypeID. if possible values are too many you can create new table to store these userTypes.
UserTypeID
1=Technician
2=Mechanic
3=Accounttant
Edit1
UserTypeID will be exist in all sub class entities.
Also from the other comments I feel lot concerns about getting data out of sync w/o explicit RI constraint. Just wanted to make sure that this column value should not be coming from app code or user instead the sql API inserting record should find out the right value based on which sub class entity is getting the insert record.
For example Pr_InsertUser API insert new technician. This insert API first finds out why I the UserTypeId for technician and insert record in to class user and get userid. Then passes the userId and UserTypeId to subclass technician an call another private sql API Pr_Insert_Technician to insert more attributes.
So the point I am trying to make is as SQL does not support explicit FK from multiple tables to single table that should be taken care in SQL API.
Declare #user Table
(
userid int
,UserTypeID Tinyint
,username sysname
,userAddress sysname
)
Declare #Technician Table
(
userid int
,UserTypeID Tinyint
,attr1 sysname
,attr2 sysname
)
Declare #Mechanic Table
(
userid int
,UserTypeID Tinyint
,attr3 sysname
,attr4 sysname
)
Declare #Accounttant Table
(
userid int
,UserTypeID Tinyint
,attr2 sysname
,attr4 sysname
)
You may want to familiarize yourself with the way ORM's do it.
Even if you don't use an ORM. It will lay out some of the options.
http://nhibernate.info/doc/nh/en/#inheritance
http://ayende.com/blog/3941/nhibernate-mapping-inheritance
I am fairly new to PowerBuilder Classic 12. I need to check whether a record is available and if not insert from a textbox. I would probably need a DataStore since someone suggested a preference to SQL statements. Thanks.
this code is behaving funny, please where is the problem? at one time it works but running the program again it accepts a data that has already been inserted. the program is not giving any error but i can see the same data stored in the table.
string id, idno
idno=trim(sle_idno.text)
if idno="" then
messagebox("EMPTY","Enter a record")
return
end if
SELECT employee.idnumber
INTO :id
FROM employee ;
if idno=id then
messagebox("AVAILABLE","Record available")
return
end if
INSERT INTO employee
( idnumber )
VALUES ( :idno ) ;
Fixing existing code
You're missing a WHERE clause; this is trying to stuff all idnumber values into id. That's why your existing code is failing.
Have a look at the help file that comes with PB. (The PDF manuals that come with it are good too, but the help file is right there on the menu of the IDE.) There are plenty of examples in there on how you should code embedded SQL statements. You should be checking the error attributes of the transaction object (in this case it is implicitly SQLCA) to determine if the transaction executed successfully or not, returned any rows, etc....
A new approach
There are several ways to approach this with a DataStore. The easiest is to make a DataWindow object against the employee table, that takes an argument and uses it in the SQL statement in the WHERE clause. In your script, set up a DataStore using this object and Retrieve() it using the idnumber as the argument, check the return value of Retrieve() (the number of rows returned if positive or zero, an error if negative) and if it's zero, InsertRow() on your DataStore, do your SetItem()'s on it (you'll want to load more than just idnumber, right?) and then do an Update() on it.
You are looking for Merge.
I will explain it using an example. Just send the values in Database via Stored Proc? and use following technique.
Sample DDL
CREATE TABLE Employee
(
EmployeeID INTEGER PRIMARY KEY,
EmployeeName VARCHAR(15)
)
CREATE TABLE EmployeeSalary
(
EmployeeID INTEGER ,
EmployeeSalary INTEGER
)
Sample DML For Employee
INSERT INTO Employee
VALUES(1,'SMITH')
INSERT INTO Employee
VALUES(2,'ALLEN')
INSERT INTO Employee
VALUES(3,'JONES')
INSERT INTO Employee
VALUES(4,'MARTIN')
INSERT INTO Employee
VALUES(5,'JAMES')
Sample DML For EmployeeDetails
INSERT INTO EmployeeSalary
VALUES(1,23000)
INSERT INTO EmployeeSalary
VALUES(2,25500)
INSERT INTO EmployeeSalary
VALUES(3,20000)
Merge Query
MERGE EmployeeSalary AS stm
USING (SELECT EmployeeID,EmployeeName FROM Employee) AS sd
ON stm.EmployeeID = sd.EmployeeID
WHEN MATCHED THEN UPDATE SET stm.EmployeeSalary = stm.EmployeeSalary + 12
WHEN NOT MATCHED THEN
INSERT(EmployeeID,EmployeeSalary)
VALUES(sd.EmployeeID,25000);
References
First Reference
Second Reference
Third Reference
Fourth Reference