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How can I use this query with the query method (SQLiteDatabase.query)?

The task I've been given is to write a query to return the number of orphaned rows. I have achieved this but another task is to then not use the rawQuery method to achieve the same result using the query method.
The issue is that I get java.lang.IllegalStateException: Invalid tables
The tables, there are 3 are
the parent table which has an _id column and a name column
the child table which has an _id column, a name column and a childtoparentlink column that is an integer that links to the parent table.
the friend table which has an _id column, a name column and a friendtochildlink column.
The SQL to create and to put rows into the tables, including some orphans is like
CREATE TABLE parent(_id INTEGER PRIMARY KEY,parentname TEXT);
CREATE TABLE child(_id INTEGER PRIMARY KEY,childname TEXT, childtoparentlink INTEGER);
CREATE TABLE friend(_id INTEGER PRIMARY KEY,friendname TEXT, friendtochildlink INTEGER);
INSERT INTO parent VALUES(null,'Parent A');
INSERT INTO parent VALUES(null,'Parent B');
INSERT INTO child VALUES(null,'Child A',1);
INSERT INTO child VALUES(null,'Child B',2);
INSERT INTO child VALUES(null,'Child X',10); -- orphan
INSERT INTO friend VALUES(null,'Friend A',1);
INSERT INTO friend VALUES(null,'Friend B',2);
INSERT INTO friend VALUES(null,'Friend X',100); -- orphan
The query that works and gives the right values when using rawQuery is
SELECT
(
SELECT count() FROM child
LEFT JOIN parent ON child.childtoparentlink = parent._id
WHERE parent.parentname IS NULL
) AS child_mismatches,
(
SELECT count() FROM friend
LEFT JOIN child ON friend.friendtochildlink = child._id
WHERE child.childname IS NULL
) AS friend_mismatches
I get two columns each with a value of 1 (as wanted).
My actual code is :-
public ArrayList<String> checkLinkIntegrity() {
ArrayList<String> return_value = new ArrayList<>();
String suffix = "_mismatches";
String child_result_cl = TB_CHILD + suffix;
String sq_child_mismatches = "(SELECT count() FROM " +
TB_CHILD +
" LEFT JOIN " + TB_PARENT +
" ON " + TB_CHILD + "." + CL_CHILDTOPARENTLINK + " = " +
TB_PARENT + "." + CL_PARENTID +
" WHERE " + TB_PARENT + "." + CL_PARENTNAME + " IS NULL)" +
" AS " + child_result_cl;
String friend_result_cl = TB_FRIEND + suffix;
String sq_friend_mismatches = "(SELECT count() FROM " +
TB_FRIEND +
" LEFT JOIN " + TB_CHILD +
" ON " + TB_FRIEND + "." + CL_FRIENDTOCHILDLINK + " = " +
TB_CHILD + "." + CL_CHILD_ID +
" WHERE " + TB_CHILD + "." + CL_CHILDNAME + " IS NULL)" +
" AS " + friend_result_cl;
String full_query = "SELECT " + sq_child_mismatches + "," + sq_friend_mismatches;
SQLiteDatabase db = this.getWritableDatabase();
Cursor csr;
Log.d("RAWQUERYSQL",full_query);
csr = db.rawQuery(full_query,null);
return_value.addAll(dumpCursorToStringArrayList(csr,"RAWQUERY"));
// Fails invalid table
csr = db.query(null,new String[]{sq_child_mismatches,sq_friend_mismatches},null,null,null,null,null);
return_value.addAll(dumpCursorToStringArrayList(csr,"SECONDTRY"));
csr.close();
return return_value;
}
and the dumpCursortoStringArrayList method is :-
private ArrayList<String> dumpCursorToStringArrayList(Cursor csr, String tablename) {
ArrayList<String> rv = new ArrayList<>();
int original_position = csr.getPosition();
csr.moveToPosition(-1);
rv.add("Table: " + tablename);
while (csr.moveToNext()) {
rv.add("\tRow # " + String.valueOf(csr.getPosition() + 1));
for (String column: csr.getColumnNames()) {
rv.add("\t\tColumn: " + column + "\tvalue is: \t" + csr.getString(csr.getColumnIndex(column)));
}
}
csr.moveToPosition(original_position);
return rv;
}
I get the same error if I try "" instead of null e.g.
If I use only the rawQuery I get
04-22 07:07:33.914 6271-6271/s.q001 I/RESULTS: Table: RAWQUERY
04-22 07:07:33.914 6271-6271/s.q001 I/RESULTS: Row # 1
04-22 07:07:33.914 6271-6271/s.q001 I/RESULTS: Column: child_mismatches value is: 1
04-22 07:07:33.914 6271-6271/s.q001 I/RESULTS: Column: friend_mismatches value is: 1
This is from using
ArrayList<String> results = DBOpenHelper.checkLinkIntegrity();
for (String s : results) {
Log.i("RESULTS",s);
}
How can I run the query with the query method instead of the rawQuery method, to get the better marks?

Your issue is that the query method expects a table as it then generates SQL as per
SELECT your_columns FROM the_table;
As there is no table it issues the Invalid Table exception.
You have to provide something that will satisfy the FROM clause, it cannot be nothing.
You can get around this in a few ways, which I guess is what the homework is trying to get you to ascertain/explore.
Fix 1
You could supply one of the tables that exist e.g. use
csr = db.query(null,new String[]{sq_child_mismatches,sq_friend_mismatches},null,null,null,null,null,"1");
Note the 8th parameter, this LIMITs the number of rows generated to one as there would be a row generated for each row in the fake table.
Fix 2
or as FROM can be a subquery (see diagram) you could use a subquery e.g. one that you have
So you could use :-
csr = db.query(
sq_child_mismatches, //<<<<<<<<<< the fake subquery
new String[]{
sq_child_mismatches,
sq_friend_mismatches
},
null ,null,null,null,null
);
In this case, as the fake subquery returns a single row/result, there is no need for the LIMIT clause.

Does the prepared-statement work this way?

I am trying to populate one table in my database with pretty complex data. For this, I am using a generator API (which gives me random data).
public void populateCrackers(){
PreparedStatement psm;
String queryJoke = "(SELECT jid FROM Jokes WHERE jid=?)";
String queryHat = "(SELECT hid FROM Hats WHERE hid=?)";
String queryGift = "(SELECT gid FROM Gifts WHERE gid=?)";
String query = "INSERT INTO Crackers(cid, name, jid, hid, gid, quantity) VALUES(" +
"?, " +
"?, " +
queryJoke + ", " +
queryHat + ", " +
queryGift + ", " +
"?)";
System.out.println(query);
String cracker_String = utils.JSONUtils.getJSON(crackerAPI, client);
JSONObject crackerJSON = new JSONObject(cracker_String);
JSONArray crackers = crackerJSON.getJSONArray("results");
for(int j=0; j<crackers.length(); j++){
try{
psm = connection.prepareStatement(query);
psm.setInt(1,crackers.getJSONObject(j).getInt("cid"));
psm.setString(2, crackers.getJSONObject(j).getString("cname"));
psm.setInt(3, crackers.getJSONObject(j).getInt("rjoke"));
psm.setInt(4, crackers.getJSONObject(j).getInt("rhat"));
psm.setInt(5, crackers.getJSONObject(j).getInt("rgift"));
psm.setInt(6, crackers.getJSONObject(j).getInt("cquantity"));
psm.execute();
System.out.println(crackers.getJSONObject(j).get("cid") + " "
+ crackers.getJSONObject(j).get("cname") + " "
+ crackers.getJSONObject(j).get("cquantity") + " "
+ crackers.getJSONObject(j).get("rjoke") + " "
+ crackers.getJSONObject(j).get("rhat") + " "
+ crackers.getJSONObject(j).get("rgift"));
}catch (Exception e){
e.printStackTrace();
}
}
}
This is the method that populates my "Crackers" tab. I am wondering if this be accepted as a prepared statement. When I run it in psql interactive command line tool, exactly that statement with some chosen ids (e.g INSERT INTO Crackers (cid, name, hid, jid, gid, quantity) VALUES('cid', 'name', (SELECT hid FROM Hats WHERE hid=11), (SELECT jid FROM Jokes where jid=99), (SELECT gid FROM Gifts WHERE gid=13), 5) it works flawlessly.
Does my preparedstatement break the Constraint?
Any ideas?
LATER EDIT: The inconsistency is the form of that null values can reach my Crackers table (e.g. Cracker(1, "hello", null, null, 3, 123) appears in the table.

There is nothing about Prepared statement. Constraint can be broken by parameters you set to it. And you can run your PLSQL statement as anonimous block in PreparedStatement as well.
Just surround it with BEGIN ... END. only one thing is different - for JDBC parameters are ? mark not :parameter as for PLSQL and there is no way to use named parameter.
That means if you need to use parameter more than once for JDBC you have to have that many ? marks and set all of them.
So, focus on parameters you pass to and their sequence.

The code is correct, though the prepared statement must be closed, and it would be better to create the statement once, before the for loop.
Now there is crackers.length() times a statement created but not closed. That might give problems.
Use the try-with-resouce syntax for automatic closing, irrespective of any exception or return.
try (PreparedStatement psm = connection.prepareStatement(query)) {
for (int j = 0; j < crackers.length(); j++) {
...
psm.executeUpdate();
And call executeUpdate instead of the more general execute. The resulting update count might be of interest (1/0).

I realised I had the wrong constraints on my table. I was letting null values in. There was nothing wrong with the prepared statement.
The right query to create the table is this one:
String createCrackersQuery = "CREATE TABLE Crackers(" +
" cid INTEGER," +
" name VARCHAR NOT NULL," +
" jid INTEGER NOT NULL," +
" hid INTEGER NOT NULL," +
" gid INTEGER NOT NULL," +
" quantity INTEGER NOT NULL," +
" CONSTRAINT Cracker_Primary PRIMARY KEY (cid)," +
" CONSTRAINT Cracker_Name_Unique UNIQUE(name)," +
" CONSTRAINT Joke_Foreign FOREIGN KEY (jid) REFERENCES Jokes(jid)," +
" CONSTRAINT Hat_Foreign FOREIGN KEY (hid) REFERENCES Hats(hid), " +
" CONSTRAINT Gift_Foreign FOREIGN KEY (gid) REFERENCES Gifts(gid)" +
")";

How to Dynamically Assign Table Name in mysql Server

I am trying To Create Tables in mysql dynamically And Assign them Name Using The Email Address User Provided. But Whenever I try to Assign Table Name dynamically it shows me error and i don,t know anyother way to fulfil my requirement.
Here is The Code I Wrote
String TableName = Email.getText();
try {
String myTableName = "CREATE TABLE '" + TableName + "' "
+ "(id INTEGER not NULL, "
+ " first VARCHAR(255), "
+ " last VARCHAR(255), "
+ " age INTEGER, "
+ " PRIMARY KEY ( id ))";;
Class.forName(m.RegisterationString);
java.sql.Connection con;
con = DriverManager.getConnection(m.URL, m.UserName, m.Password);
Statement State = con.createStatement();
//This line has the issue
State.executeUpdate(myTableName);
System.out.println("Table Created");
}

In MySQL the name of table should not be between '' it can be between :
String myTableName ="CREATE TABLE `" + tableName + "`"
//--------------------------------^-----------------^
Note for good pratice don't start the name of variable with upper letter like State or TableName, Email

Convert PostgreSQL Serial Primary Key to Oracle Statement

I have a java file that connects to a database and this is the code:
package movies;
import java.sql.*;
public class CreateTable {
public static void main(String args[]) {
Connection c = null;
Statement stmt = null;
String sql;
try {
Class.forName("oracle.jdbc.OracleDriver");//driver
c = DriverManager.getConnection("jdbc:oracle:thin:#localhost:1521/XE", "username", "password");//PUT DATABASE CONNECTION INFO
System.out.println("Opened database successfully from within CreateTable.java");
stmt = c.createStatement();
sql = "CREATE TABLE MOVIES "
//+ "(ID SERIAL PRIMARY KEY,"//can't figure out this statement and it works if I comment it out.
+ " (NAME NVARCHAR2(255) PRIMARY KEY,"//I don't want this to be the primary key.
+ " YEAR NVARCHAR2(255),"
+ " RATING NVARCHAR2(16),"
+ " ACTORS NVARCHAR2(1024))";
stmt.executeUpdate(sql);
stmt.close();
c.close();
} catch (Exception e) {
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
System.out.println("Table created successfully");
}
}
The commented part is where I'm running into problems. I'm trying to convert a PostgreSQL statement to an Oracle 11g XE statement. I would like to have an ID with a sequential number to identify it. (ie. 0001, 0002, 0003, etc.) How can I do this? Could you provide an example? I'm at a loss right now. I'm using Netbeans 8.02, Oracle 11g XE, and Apache Tomcat 8.0.15.0.
edit I'm trying to have the ID column as the only primary key. I would eliminate the NAME column as a primary key and make the ID column the new primary key.

I don't think you can have two separate columns with primary key like that, if you want a primary key on two columns use,
edit :
sql = "CREATE TABLE MOVIES "
+ "(ID INT PRIMARY KEY," -- CHANGES
+ " NAME NVARCHAR2(255),"
+ " YEAR NVARCHAR2(255),"
+ " RATING NVARCHAR2(16),"
+ " ACTORS NVARCHAR2(1024))";
i have created the table to show the syntax works in oracle now..
SQL> create table movies
2 (id int primary key,
3 name NVARCHAR2(255),
4 year NVARCHAR2(255),
5 rating NVARCHAR2(255),
6 actors NVARCHAR2(1024));
Table created.

This code worked. See the comments below to view the changes:
try {
Class.forName("oracle.jdbc.OracleDriver");//driver
c = DriverManager.getConnection("jdbc:oracle:thin:#localhost:1521/XE", "username", "password");//PUT DATABASE CONNECTION INFO
System.out.println("Opened database successfully from within CreateTable.java");
stmt = c.createStatement();
sql = "CREATE TABLE MOVIES "
//THE FOLLOWING LINE WAS CHANGED:
+ "(\"ID\" INTEGER PRIMARY KEY, \"TYPE\" VARCHAR2(32),"
+ " NAME NVARCHAR2(255),"
+ " YEAR NVARCHAR2(255),"
+ " RATING NVARCHAR2(16),"
+ " ACTORS NVARCHAR2(1024))";
//THE FOLLOW TWO STATEMENTS WERE ADDED:
String sql1 = "CREATE SEQUENCE MOVIES_SEQ START WITH 1 INCREMENT BY 1 NOMAXVALUE";
String sql2 = "CREATE TRIGGER MOVIES_TRIGGER BEFORE INSERT ON MOVIES FOR EACH ROW BEGIN SELECT MOVIES_SEQ.NEXTVAL INTO :NEW.ID FROM DUAL; END;";
stmt.executeUpdate(sql);
//THESE TWO WERE ALSO ADDED:
stmt.executeUpdate(sql1);
stmt.executeUpdate(sql2);
stmt.close();
c.close();
} catch (Exception e) {
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}

Copy values from one table to another with 'where' condition

I want to copy values from songDetails table to playlistDetails table.
here is my code :
public void transferData(String name) {
SQLiteDatabase db = this.getWritableDatabase();
String selectQuery = "INSERT INTO "+ TABLE_CURRENTLIST + " SELECT * FROM " + TABLE_DATA + " WHERE " + KEY_ALBUMNAME+ " = " + name + "";
db.execSQL(selectQuery);
}
While executing this code, it throws this exception
01-31 01:29:49.426: E/AndroidRuntime(3102): android.database.sqlite.SQLiteException: no such column: unknown (code 1): , while compiling: INSERT INTO PlayListDetails SELECT * FROM songDetails WHERE albumName = unknown
the value of 'name' variable is correct. And i want to copy only the rows which have the albumName as unknown.
I'm struggled with this. Please help me.

You are missing single quotes around query param value (unknown).
Your query should be
String selectQuery = "INSERT INTO "+ TABLE_CURRENTLIST + " SELECT * FROM " + TABLE_DATA + " WHERE " + KEY_ALBUMNAME+ " = '" + name + "'";
My suggestion would be to use PreparedStatement style parameters.