String link = "http://hosted.ap.org";
I want to find whether the given url is already existing in the SQL DB under the table name "urls". If the given url is not found in that table i need to insert it in to that table.
As I am a beginner in Java, I cannot really reach the exact code.
Please advise on this regard on how to search the url in the table.
I am done with the SQL Connection using the java code. Please advise me on the searching and inserting part alone as explained above.
PreparedStatement insert = connectin.preparedStateme("insert into urls(url) vlaues(?)");
PreparedStatement search = connectin.preparedStateme("select * from urls where url = ?");
search.setString(1, <your url value to search>);
ResultSet rs = search.executeQuery();
if (!rs.hasNext()) {
insert.setString(1, <your url value to insert>);
insert.executeUpdate();
}
//finally close your statements and connection
...
i assumed that you only have one field your table and field name is url. if you have more fields you need to add them in insert query.
You need to distinguish between two completely separate things: SQL (Structured Query Language) is the language which you use to communicate with the DB. JDBC (Java DataBase Connectivity) is a Java API which enables you to execute SQL language using Java code.
To get data from DB, you usually use the SQL SELECT statement. To insert data in a DB, you usually use the SQL INSERT INTO statement
To prepare a SQL statement in Java, you usually use Connection#prepareStatement(). To execute a SQL SELECT statement in Java, you should use PreparedStatement#executeQuery(). It returns a ResultSet with the query results. To execute a SQL INSERT statement in Java, you should use PreparedStatement#executeUpdate().
See also:
SQL tutorial
JDBC tutorial
Related
I want to update two sql tables at once in java. I'm using SQLiteManager. Could someone please suggest a way of doing that?
Assuming you have the driver and connection to the database, you should be able to run most sql commands from java. There is not a single sql statement that will update two tables at once but you can update each table in turn which will have the same effect.
See http://www.javaworkspace.com/connectdatabase/connectSQLite.do for some examples.
For a table update, use
statement.execute(sql);
where sql is a string of the form
sql = "UPDATE myTable SET myColumn = newValue WHERE someOtherColumn=value";
I need to initialize a database from my Java application. For reasons of code maintainability, I would like to maintain the SQL code separately from the Java code (it is currently in a separate source file).
The first few lines of the file are as follows:
-- 1 - Countries - COUNTRIES.DAT;
drop table Countries if exists;
create table Countries(
CID integer,
ECC varchar(2),
CCD varchar(1),
NAME varchar(50));
I read the SQL code from the file and store it in a string. Then I do:
PreparedStatement stmt = dbConnection.prepareStatement(sqlString);
This fails with the following exception:
java.sql.SQLSyntaxErrorException: unexpected token: CREATE : line: 2
This looks as if JDBC doesn't like multiple SQL statements in a single PreparedStatement. I have also tried CallableStatement and prepareCall(), with the same result.
Does JDBC provide a way to pass the entire SQL script in one go?
The JDBC standard (and the SQL standard for that matter) assumes a single statement per execute. Some drivers have an option to allow execution of multiple statements in one execute, but technically that option violates the JDBC standard. There is nothing in JDBC itself that supports multi-statement script execution.
You need to separate the statements yourself (on the ;), and execute them individually, or find a third-party tool that does this for you (eg MyBatis ScriptRunner).
You might also want to look at something like flyway or liquibase.
To run a hardcoded / loaded from file queries you can use execute like:
Statement stmt = null;
String query = "drop table Countries if exists;
create table Countries(
CID integer,
ECC varchar(2),
CCD varchar(1),
NAME varchar(50));";
try {
stmt = con.createStatement();
stmt.execute(query);
} catch (SQLException e ) {
JDBCTutorialUtilities.printSQLException(e);
} finally {
if (stmt != null) { stmt.close(); }
}
If you want to run dynamic queries for example to append values you have to use PreparedStatement. For running a query from a file it's not recommended to put dynamic queries in it.
I want to display the data of a postgresql database using the CRUD in the play framework; I looked for any examples to get idea which I didn't find after a long time of searching in google. Someone help me with this if you can or post a valid link regarding this. Thanks in advance!
I use, Play 1.2.5, java and postgresql.
I assume you want to do this in your application code in runtime.
You can execute query using DB plugin to search DB metadata using native PostgreSQL queries.
Here's an example how to get column names of my system DOCUMENT table:
List<String> columns = new ArrayList<>();
ResultSet result = DB.executeQuery("select column_name from INFORMATION_SCHEMA.COLUMNS where table_name = 'DOCUMENT';");
while(result.next()) {
String column = result.getString(1);
columns.add(column);
}
This note that code is somewhat simplified and you should use prepared statements if anything in this query will be inserted from data that user or any other system entered.
Use DB.getConnection().prepareStatement() to get PreparedStatement instance.
I want to run a native SQL from a file using Hibernate. The SQL can contain several statements creating the database structure (i.e. tables, constraints but no insert/update/delete statements).
Example, very simple query is below (which contains the following two SQL statements)
CREATE DATABASE test;
CREATE TABLE test.testtbl( id int(5));
I am using MySQL db, and when I run the above query I am gettng syntax error returned. When I run them one by one, its ok.
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:
You have an error in your SQL syntax; check the manual that corresponds to your
MySQL server version for the right syntax to use near
'CREATE TABLE test.testtbl( id int(5))' at line 1
The code to run the query is below (above statement is assigned to 'sql' variable):
session = sf.openSession();
session.beginTransaction();
Query qry = session.createSQLQuery(sql);
qry.executeUpdate();
session.getTransaction().commit();
Any help would be appreciated.
As others have explained
You must run these queries one by one.
The hibernate code gets translated into running one update statement on JDBC.
But you provided two update statements.
In addition,
I personally prefer to have the code that creates tables outside of the Java application, in some DB scripts.
The parameters of the method createSQLQuery is t-sql code;
t-sql code to ensure that in the mysql interface analyzer correctly.
You can try changed the sql :'CREATE TABLE testtbl(id int(5));'
by the way you can use JDBC Connection api (Don't recommend to do so)
Such as:
java.sql.Connection conn=session.connection();
Hi at now i am programming with Java and wanting to insert some value to specific column choosen. Also, i want to add it in parameter similar with C#:
example:
SqlCommand cmdb = new SqlCommand("insert into Assignment1(textname,person,date,text)
values (#textName,#person,#date,#text)", con);
cmdb.Parameters.AddWithValue("#textname", textPathLabel.Text);
cmdb.Parameters.AddWithValue("#person", personNameTB.Text);
cmdb.Parameters.AddWithValue("#date", DateTime.Now);
cmdb.Parameters.AddWithValue("#text", theBytes);
What you need is to use PreparedStatement in Java. With the example that you've, the corresponding PreparedStatement would look something like this:
PreparedStatement ps = connection.prepareStatement("insert into Assignment1(textname,person,date,text) values(?,?,?,?)");
You would then use the appropriate ps.setXX() methods to set the appropriate values for the parameters that you've defined and then call ps.executeUpdate() to execute the call to the database.
The "JDBC(TM) Database Access" would be a good place to start learning about how to use or execute common SQL statements, and perform other objectives common to database applications.