How do you query database using a variable? Dynamic SQL...?

Question

I'm wondering how to search a database table using a given variable or an array in the SQL query. I'm currently using Java and PostgreSQL and I want to do something like:

String word = "Apples";
SELECT * FROM table WHERE name = word;

or

token[0] = "Apples";
SELECT * FROM table WHERE name = token[0};

Does anyone know the correct way to do this?

My eventual goal is simply to check the database to see if a word that a user has input is stored in the database and if it is then do something with that word.

jdbc.postgresql.org/documentation/head/query.html

Serg
– Serg

2016-05-19 07:03:37 +00:00
Commented May 19, 2016 at 7:03 — Serg
– Serg, Commented May 19, 2016 at 7:03

Dibakar Paul · Accepted Answer · 2016-05-19 07:08:05Z

3

Use PrepareStatement like,

String word = "Apples";
PreparedStatement st = conn.prepareStatement("SELECT * FROM table WHERE name = ?");
st.setString(1, word);
ResultSet rs = st.executeQuery();

answered May 19, 2016 at 7:08

Dibakar Paul

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3 Comments

Feenix Over a year ago

When I try this I get the error message: error: cannot find symbol PreparedStatement st = conn.prepareStatement("SELECT * FROM table WHERE name = ?");

user330315 Over a year ago

@Feenix: docs.oracle.com/javase/6/docs/technotes/guides/jdbc/getstart/…

Dibakar Paul Over a year ago

Is it compile time exception or runtime? Did you import, import java.sql.PreparedStatement;

Sanghita · Accepted Answer · 2016-05-19 07:07:05Z

0

If you want to fetch data in java end, do something like:

Connection con = DriverManager.getConnection
  ("jdbc:derby://localhost:1527/testDb","name","pass");
  PreparedStatement updateemp = con.prepareStatement
  ("insert into emp values(?,?,?)");
  updateemp.setInt(1,23);
  updateemp.setString(2,"Roshan");
  updateemp.setString(3, "CEO");
  updateemp.executeUpdate();
  Statement stmt = con.createStatement();
  String query = "select * from emp";
  ResultSet rs =  stmt.executeQuery(query);

See full details : Here

answered May 19, 2016 at 7:07

Sanghita

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