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Universal query to check whether a table exist in all RDBMS

I have searched a lot but i could not find a query which will apply to any RDBMS to check whether a table exits. Some are ok with mysql and h2 but its not compatible with oracle. Any one has a solution for this.
This works for oracle but not h2 or mysql
select count(*) as tblCount from user_tables where table_name = 'ALERTS_HISTORY';

The java.sql.DatabaseMetaData object (which is obtainable from a Connection via .getMetaData() has a getTables(…) function, which does what you want; the driver will care about the SQL.

How to display a database columns using CRUD in play framework?

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.

Hibernate multiple native SQL statements

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();

Hibernate session.createQuery error while replace method with single quote

I got very typical issue. My dynamically generated query like this...
UPDATE Templates t SET t.TEMPLATE_DATA = replace(t.TEMPLATE_DATA, 'Test\'s Test', 'Kent"s Test'), t.TEMPLATE_DATA = replace(t.TEMPLATE_DATA, 'Test"s Test', 'Kent"s Test'), UPDATE_DATE = NOW() where PRACTICE_ID = 1 AND CATEGORY_ID IN (1)
This works perfect when I explictily fire this query in db. but by using hibernate's session.createQuery(-- my query --) if thwows an error QueryTranslatorException.
Database : Mysql 5.3
Have any one faced this issue?
Thanks in advance.

Try to run this in Hibernate as native SQL query:
session.createSQLQuery(-- query text --);
Because if you use
session.createQuery(-- query text --);
Hibernate will try to execute it as HQL query which differs from usual SQL query.
HQL is object oriented query language. It operates in terms of objects rather then in terms of tables. Here posted a brief description of difference between SQL and HQL. But if you have time better to read appropriate sections of hibernate's documentation about HQL and Native SQL usage.

If you want to execute SQL Query in hibernate, Use : session.createSQLQuery(String query);

How to search and insert a value using java code?

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