Helo,
I am a beginner java programmer.
I need to update multiple rows with a query using mysql database and java codes.
I need to update the age field (data type int) in the database based on the current date. I believe I need to iterate and use the hasnext ... but I just unable.
If you need to update all the rows using a common logic based on current date, write a single update query and execute it. It will update all the rows. If logic is different then use updatble result set.
Are you facing a problem in executing an update query or is it with the iteration on integer array. Please provide more details. And if you are attempting to update similar data, try doing it using a single query, as executing queries in loop is not recommended.
Related
I am currently trying to push some data from Java into BigQuery, in order to be able to make use of it only for the next query and then to get rid of it.
The data consists of 3 columns which exists in the table I want to query. Therefore, by creating a temporary table containing this data, I could make a left join and get the query results I am in need of.
This process will happen on a scheduled basis, having different sets of data.
Can you please tell me if that can be done ?
Many thanks !
Using the jobs.query API, you can specify a destinationTable as part of configuration.query. Does that help? You can control the table expiration time using the tables.update API and setting expirationTime.
Alternatively, you can "inline" the table as part of the query that you want to run using a WITH clause in standard SQL rather than writing to a temporary table.
I want to insert data to TERADATA with jdbc.But it is slow. How can I make it faster?
I wrote this code:
connection_tera= DriverManager.getConnection
(
"jdbc:teradata://192.168.x.xx/database=DBC,tmode=ANSI,charset=UTF8","dbc","dbc"
);
stmt_tera = connection_tera.prepareStatement("insert into a.b values(?)");
//some code here to start while loop
stmt_tera.setObject(i,reset.getobject(i));
stmt_tera.addBatch();
if(addedBatchNumber%100==0)
stmt_tera.executeBatch();
connection_tera.commit();
stmt_tera.clearBatch();
//some code here and finish while loop
Should I add paramater like TYPE=FASTLOAD to connection string? or something else?
If you are loading to an empty table I would consider using JDBC FastLoad. For more details on the performance of JDBC to insert data into a Teradata table please refer to the following article on the Teradata Developer Exchange: Speed up your JDBC/ODBC Applications
If your table is not empty, it may make sense to load the data to a staging (intermediate) table that is empty first. Then use the ANSI MERGE operation to apply the INSERT/UPDATE logic to the target table. The MERGE operation will perform faster than the traditional INSERT and UPDATE statements because the operation works at the block level instead of row level. In some instances you can even avoid spooling the source data before the data is applied to the target table.
Here is a collection of sample Teradata JDBC Driver programs. Programs 205 through 209 are examples of using FastLoad.
Additionally you can also consider another side of the coin..Meaning you can think of performing multiple row insert with single query
insert into table1 (First,Last) values ('Fred','Smith'),
('John','Smith'),
('Michael','Smith'),
('Robert','Smith');
The benefits are
Connecting/interacting with database is an expensive operation. Say you have to insert 100 rows using your code so you would write your application in such a way to fire 100 quires( 100 db interactions ).. Instead of this, build your sql query as mentioned above and try insert and check the performance.
You are avoiding n number of database interactions.
Insert operation is seamlessly faster if you do like this.. This has been widely adopted technique to restore/import databases.
Hope this will be helpful..
Cheers!
Cheers!
If I'm reading this correctly, you are executing and committing a batch that has only one insert statement in it - I don't think that is your intention ( or, if it is, I think you are misunderstanding how batches are expected to be used )
Seems like you need to have an inner loop that adds an arbitrary number of statements to the batch which you then submit via executeBatch()
I have a producer thread in Java pulling items from an Oracle table every n milliseconds.
The current implementation relies on a Java timestamp in order to retrieve data and never re-retrieve them again.
My objective is to get rid of the timestamp pattern and directly update the same items I'm pulling from the database.
Is there a way to SELECT a set of items and UPDATE them at the same time to mark them as "Being processed"?
If not, would a separate UPDATE query relying on the IN clause be a major performance hit?
I tried using a temporary table for that purpose, but I've seen that performance was severely affected.
Don't know if it helps, but the application is using iBatis.
If you are using oracle 10g or higher, you can use the RETURNING clause of the update statement. If you wish the retrieve more than one row you can use the BULK COLLECT statement.
Here is a link to some examples;
http://psoug.org/snippet/UPDATE-with-RETURNING-clause_604.htm
I have this table in oracle and i need to retrieve two columns from the table desc_data
eg:
select ticket_id, date_logged from desc_data;
I would have around 10,000 records in this table, so if I do this operation from java and perform some operations in java by putting these values in a list and then based on some conditions filter data and insert back into some other table, would it be possible and if it's possible would it be an overhead?
I think better to use a stored procedure in database and just call it from java. But what you consider is a possible solution too.
It depends on what type of filtering you wish to do on your 10000 records. If the filtering is simple, such as filtering the records in a date range, then you can achieve that just using SQL. If your processing is more complex, then you could also use an stored procedure. As you are running on Oracle these can be written in Java. See here for an example.
I am just getting into ibatis with SqlMap for the first time and I have run into a problem. I have figured out how to insert, delete, update, and select single records. Now however I am trying to write a select statement that will bring back more than a single record and I am getting mapping errors. How do I specify that the result should be a List of my custom objects?
I've figured it out. Using java I simply had to use the queryForList function instead of queryForObject.