Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

Dynamic SQL in Java

Posted on 2004-10-12
7
Medium Priority
?
349 Views
Last Modified: 2010-03-31
Folks,

I am using prepared statement on one of my java calls to the database.

Here's is a sample of the same

 String sql = "Select <table_nam>.<column_name> from  <schema_name>.<table_name>
 
 where <condition>"
         and <column_name_1> = ? "                        +
        " and <column_name_2> = ? "                     +
        " and <column_name_3> = ? ";
          
          
I set the parameters for aboe column as below

stmt.setString( 1, column1 );
stmt.setString( 2, column2 );
stmt.setString( 3, column3 );

column1, column2 and column3 values are passed to the method that has the above code block.

Question:

How to make this SQL dynamic ?. If column1, column2 and column3 has particular values (say "X") I DO NOT want to add
in the SQL. For that I have an if statment and populate sql without problem. BUT i have to incorporate many permutations
for setting the statement block, so that it matches with the SQL string. How to do both things i.e generating SQL and setting values (when the values are conditional) in statements.

What is the best possible solution to have the code modular and more robust (avoiding lot of if's)

0
Comment
Question by:Java_Problem
  • 3
  • 2
5 Comments
 
LVL 9

Expert Comment

by:doronb
ID: 12288910
I usually cache my SQL PreparedStatements according to a key composed from the operation (INSERT/UPDATE/DELETE etc..) and the name/type of parameters.  This way, when I first use the query, I create it and cache it, the 2nd time and everytime after that, I simply fetch the PreparedStatement from my cache, set the parameter values and execute.
0
 

Author Comment

by:Java_Problem
ID: 12289850
Can u explain on the context of sample sql i gave in my question.
0
 
LVL 9

Accepted Solution

by:
doronb earned 500 total points
ID: 12290354
1) All of the parameters you've put between '<' and '>' are values used to produce a key to chache the statement.
2) Upon a request to execute the query, you compose the key and check if the statement is already cached.
3) If the statement isn't cached, you create the statement by bulding the SQL String, then create a PreparedStatement from the SQL String.
4) Once the query is cached, you fetch it from the cache and bind the values into their respective places.
5) Execute the PreparedStatement after binding the values and get the ResultSet.

Important Note:  As far as I know, SQL (ANSI-92 compatible) doesn't allow certain values to be bound into PrepareStatements, so parameters like the condition, table-name and column-names would be impossible to bind with stmt.setXXX(...) methods, what I do here is use Java's text formatting to create the SQL String where I can simply pass some parameters as a part of the SQL String (formatted in) and other parameters as bound values for the PreparedStatement.
0
 

Author Comment

by:Java_Problem
ID: 12290842
are these 5 steps really required or there is even better approach.. I will still have "GURU's" share their views and comments (please use some example/template to explain it better)..Thanks
0
 
LVL 9

Expert Comment

by:doronb
ID: 12302705
I can hardly imagine any other way to do it given how JDBC and SQL work together.  I've seen solutions that re-created the SQL statement from scratch everytime a query had to be executed, but that's not what I think you want. :)
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

After being asked a question last year, I went into one of my moods where I did some research and code just for the fun and learning of it all.  Subsequently, from this journey, I put together this article on "Range Searching Using Visual Basic.NET …
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d…
Viewers learn about the scanner class in this video and are introduced to receiving user input for their programs. Additionally, objects, conditional statements, and loops are used to help reinforce the concepts. Introduce Scanner class: Importing…
The viewer will learn how to implement Singleton Design Pattern in Java.
Suggested Courses
Course of the Month15 days, 18 hours left to enroll

580 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question