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Saving data in a for loop in dynamoDB AWS

I have to save data in 6 tables in dynamoDB AWS, can I put a 'for' loop and save one by one as shown below :-
DynamoDBMapper mapper = new DynamoDBMapper(dynamoDB);
for(i=0;i<6;i++)
{
mapper.save(<TABLE 1 DATA>)
// and loop and save data in every table
}
Does it looks fine or it can create some problem as I am doing data base operation in loop?
My tables are very small(5 columns)
Thanks
Kailash

Running in the for loop is a bad idea and you can use the batch write item api. dynamoDB.batchWriteItem(TableWriteItems... yourMultipleTableWriteItems)

If you only need to download the data from the table into a local file, like CSV, for example, you can use this CLI tool https://github.com/zshamrock/dynocsv to export data from your table into the CSV file.

Read the table data from the PDF file and save in the MySQL database as it is

I have a requirement to read the value form a PDF file and save the result in a db.
I have converted Pdf to text .
Now the text data looks like this:
Test Name Results Units Bio. Ref. Interval
LIPID PROFILE, BASIC, SERUM
Cholesterol Total 166.00 mg/dL <200.00
Triglycerides 118.00 mg/dL <150.00
My requirement is to read the table data from the Pdf file and save in the MySQL database as it is.

use java io to read the text file and jdbc to safe the information in the mysql via sql.

Create single xml file from multiple xmls

My requirement is as follows:
I would like to use a JDBC to connect the Oracle which has xml as a table column and retrieve the records. I want all those retrieved xml records to be in one file.
I will parse those extracted xmls using JAXB API and delete some of the tags for every xml i read . Then i would like to generate one single output file which consist of all the xmls that are edited
After retrieving the data from the table my output should look like this
Extracted_records.txt
<Record><tag1></tag1><tag2></tag2><tag3></tag3><Record>
<Record><tag1></tag1><tag2></tag2><tag3></tag3><Record>
<Record><tag1></tag1><tag2></tag2><tag3></tag3><Record>
<Record><tag1></tag1><tag2></tag2><tag3></tag3><Record>
After parsing and deleting the records my output file should look like this
Outputfile.txt
<Record><tag2></tag2><tag3></tag3><Record>
<Record><tag1></tag1><tag2></tag2><Record>
<Record><tag1></tag1><Record>
<Record><tag1></tag1><tag3></tag3><Record>

Cannot read data from newly uploaded Excel file

I'm working on a system where the users need to be able to upload an excel file to the server, then the system needs to process the excel file to load data into the XMPie uProduce system.
I already have it working to load CSV files into the system. I can confirm that the excel files have been uploaded to the server successfully. However, when my program then tries to access the excel file in order to read the data, it gets this error:
The Microsoft Jet database engine could not find the object 'Sheet1'. Make sure the object exists and that you spell its name and the path name correctly.
I am setting the filter as:
select * from [Sheet1]
I have also tried it as:
select * from [filename.xls]
Neither have worked. Does anyone have any suggestions what the SQL filter should be for pulling data from a database?

Try this..
Writing an Excel query is as similar as writing a query in any other traditional data storage like SQL Server, Oracle, etc. However there are a few differences. First, you have to specify your sheet name instead of your table name. Next, you have to give starting and end cell references. Watch my following code carefully:
SELECT * FROM [users$A1:F500]
Here users is the spread sheet name.

When specifying Excel sheet names in an SQL query via ADO or similar, you have to put a $ symbol at the end of the sheet name. Try:
SELECT * FROM [Sheet1$]
More info here

file (not in memory) based JDBC driver for CSV files

Is there a open source file based (NOT in-memory based) JDBC driver for CSV files? My CSV are dynamically generated from the UI according to the user selections and each user will have a different CSV file. I'm doing this to reduce database hits, since the information is contained in the CSV file. I only need to perform SELECT operations.
HSQLDB allows for indexed searches if we specify an index, but I won't be able to provide an unique column that can be used as an index, hence it does SQL operations in memory.
Edit:
I've tried CSVJDBC but that doesn't support simple operations like order by and group by. It is still unclear whether it reads from file or loads into memory.
I've tried xlSQL, but that again relies on HSQLDB and only works with Excel and not CSV. Plus its not in development or support anymore.
H2, but that only reads CSV. Doesn't support SQL.

You can solve this problem using the H2 database.
The following groovy script demonstrates:
Loading data into the database
Running a "GROUP BY" and "ORDER BY" sql query
Note: H2 supports in-memory databases, so you have the choice of persisting the data or not.
// Create the database
def sql = Sql.newInstance("jdbc:h2:db/csv", "user", "pass", "org.h2.Driver")
// Load CSV file
sql.execute("CREATE TABLE data (id INT PRIMARY KEY, message VARCHAR(255), score INT) AS SELECT * FROM CSVREAD('data.csv')")
// Print results
def result = sql.firstRow("SELECT message, score, count(*) FROM data GROUP BY message, score ORDER BY score")
assert result[0] == "hello world"
assert result[1] == 0
assert result[2] == 5
// Cleanup
sql.close()
Sample CSV data:
0,hello world,0
1,hello world,1
2,hello world,0
3,hello world,1
4,hello world,0
5,hello world,1
6,hello world,0
7,hello world,1
8,hello world,0
9,hello world,1
10,hello world,0

If you check the sourceforge project csvjdbc please report your expierences. the documentation says it is useful for importing CSV files.
Project page

This was discussed on Superuser https://superuser.com/questions/7169/querying-a-csv-file.
You can use the Text Tables feature of hsqldb: http://hsqldb.org/doc/2.0/guide/texttables-chapt.html
csvsql/gcsvsql are also possible solutions (but there is no JDBC driver, you will have to run a command line program for your query).
sqlite is another solution but you have to import the CSV file into a database before you can query it.
Alternatively, there is commercial software such as http://www.csv-jdbc.com/ which will do what you want.

To do anything with a file you have to load it into memory at some point. What you could do is just open the file and read it line by line, discarding the previous line as you read in a new one. Only downside to this approach is its linearity. Have you thought about using something like memcache on a server where you use Key-Value stores in memory you can query instead of dumping to a CSV file?

You can use either specialized JDBC driver, like CsvJdbc (http://csvjdbc.sourceforge.net) or you may chose to configure a database engine such as mySQL to treat your CSV as a table and then manipulate your CSV through standard JDBC driver.
The trade-off here - available SQL features vs performance.
Direct access to CSV via CsvJdbc (or similar) will allow you very quick operations on big data volumes, but without capabilities to sort or group records using SQL commands ;
mySQL CSV engine can provide rich set of SQL features, but with the cost of performance.
So if the size of your table is relatively small - go with mySQL. However if you need to process big files (> 100Mb) without need for grouping or sorting - go with CsvJdbc.
If you need both - handle very bif files and be able to manipulate them using SQL, then optimal course of action - to load the CSV into normal database table (e.g. mySQL) first and then handle the data as usual SQL table.