I'm currently making a code that uses a database. This is the class of the database:
public class ScriptDLL {
public static String getCreateTableCliente(){
StringBuilder sql = new StringBuilder();
sql.append(" CREATE TABLE IF NOT EXISTS CLIENTE (");
sql.append(" CODIGO INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,");
sql.append(" NOME VARCHAR (250) NOT NULL DEFAULT (''),");
sql.append(" ENDERECO VARCHAR (255) NOT NULL DEFAULT (''),");
sql.append(" EMAIL VARCHAR (200) NOT NULL DEFAULT (''),");
sql.append(" TELEFONE VARCHAR (20) NOT NULL DEFAULT ('') )");
return sql.toString();
}
}
Ok, so i want to make a SQLite code to set CODIGO back to 1. How could i write this code?
Thanks!
I would suggest to increment the version by 1 and the old table is dropped and new table is created, this will avoid failure due to uniqueness constraint if records already exist in the table(you take care of migration ofcourse). If you have specific need just to reset codigo then try the below code. It resets the value to 1 in the internal sqllite record SQLITE_SEQUENCE.
Refer documentation which explains more about autoincrement and SQLITE_SEQUENCE : https://sqlite.org/autoinc.html
public static String resetKey(){
return "UPDATE SQLITE_SEQUENCE SET seq = 1 WHERE name = CLIENTE";
}
If this is just a one-off then just Delete the App's data, or uninstall the App and rerun.
If you want to do this frequently (ignoring the fact that relying upon the column being specific values most likely indicates a flaw in the design) then:-
You could DROP and recreate the table as is often done in the onUpgrade method of the Database Helper. Doing this in the onUpgrade method could be problematic/complicated if you had multiple tables and potentially even more complicated if you had multiple versions.
You could have a specific method such as :-
public void resetCODIGO() {
this.getWritableDatabase.execSQL("DROP TABLE IF EXISTS CLIENTE;");
this.getWritableDatabase.execSQL(getCreateTableCliente());
}
DROPing a table will result in the respective row in the sqlite_sequence table being deleted by SQLite.
The sqlite_sequence table has a row per table that has a column with AUTOINCREMENT (only 1 allowed per table).
the sqlite_sequence table has two defined columns name for the table name and seq for the last inserted sequence number.
Another solution that would involve DROP and CREATE BUT does involve updating the sqlite_sequence table could be to delete all rows from the table and to then delete the respective row in the sqlite_sequence table.
Thus alternately you could have :-
public void resetCODIGO() {
this.getWritableDatabase.delete("CLIENTE");
String whereclause = "name=?";
String[] whereargs = new String[]{"CLIENTE"};
this.getWritableDatabase.delete(
"sqlite_sequence",
whereclause,
whereargs
);
}
Note the above code is in-principle code and hasn't necessarily been tested, so it may contain some errors.
Related
I created a java class with the same name as a table from a SQL database, and using the retrieved information from that table I created multiple objects out of that Java class, and stored them inside An ArrayList.
CREATE TABLE `orderdetails` (
`orderNumber` int(11) NOT NULL,
`productCode` varchar(15) NOT NULL,
`quantityOrdered` int(11) NOT NULL,
`priceEach` decimal(10,2) NOT NULL,
`orderLineNumber` smallint(6) NOT NULL,
PRIMARY KEY (`orderNumber`,`productCode`),
KEY `productCode` (`productCode`),
CONSTRAINT `orderdetails_ibfk_1` FOREIGN KEY (`orderNumber`) REFERENCES `orders` (`orderNumber`),
CONSTRAINT `orderdetails_ibfk_2` FOREIGN KEY (`productCode`) REFERENCES `products` (`productCode`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
tuples have repeating orderNumbers, for example:
(10100,'S18_1749',30,'136.00',3),
(10100,'S18_2248',50,'55.09',2),
(10100,'S18_4409',22,'75.46',4),
Each tuple is then turned into a java object of the class with the same name as the table, and to be stored inside an Arraylist.
public ArrayList<OrderDetails> getOrders(String tableName) throws SQLException{
ArrayList<OrderDetails>od=new ArrayList<OrderDetails>();
try {
String query="SELECT * FROM "+tableName;
Statement s= con.createStatement();
ResultSet rs= s.executeQuery(query);
while(rs.next()) {
int orderNumber=rs.getInt("orderNumber");
String productCode=rs.getString("productCode");
int quantityOrdered=rs.getInt("quantityOrdered");
double priceEach=rs.getDouble("priceEach");
int orderLineNumber=rs.getInt("orderLineNumber");
OrderDetails temp=new OrderDetails(orderNumber, productCode, quantityOrdered, priceEach, orderLineNumber);
od.add(temp);
}
}
catch(SQLException e) {
System.out.println("SQL exception happened while retriving data, close connection");
throw new RuntimeException(e);
}
return od;
}
I am trying to Loop through the ArrayList and output the total amount of value (priceEach times quantityOrdered )for each checkNumber. But if I simply just loop through the ArrayList one object by object, that isn't going to work. As I will simply see the sum for each object, not each checkNumber, on the console.
ArrayList<OrderDetails>od= this.getOrders("orderdetails");
for(int i=0;i<=od.size();i++) {
System.out.println(od.get(i).getPriceEach()*od.get(i).getQuantityOrdered());
}
I'm expecting something like this to show up on console (no repeating checkNumber)
CheckNumber 10100, total value: 8494.62 (if you add up the product between priceEach and quantityOrdered for the three tuples shown above earlier in my question is the rsult)
In short is there a way for me to combine objects with repeating attributes into one?
I apologize if my question seems very vague and you don't know exactly what the problem is.
It would be greatly appreciated if you try to reach out for me and ask for further clarifications, sometimes it is very difficult to describe a problem that's too specific..
Why not simply do the computation in the database? SQL is a set-based language that is very efficient at this type of operation, compared to an iterative loop in Java.
Consider the following aggregate query:
select orderNumber, sum(quantityOrdered * priceEach) totalValue
from mytable
group by orderNumber
This gives you one record per order, with the total value over all corresponding rows.
I tried already all what i found here in Stackoverflow but nothing helped me thats is why im asking once more. I try to make a database with sqlite in android but when i opened my database to see what my programm saved i have by this foreign key always the value null.
Here is my code:
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_PERSON +" (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, IDENTIFICATION INTEGER)");
db.execSQL("create table " + TABLE_LOCATION +" (ID INTEGER PRIMARY KEY AUTOINCREMENT, LOCATION TEXT, EMPLOYEE INTEGER , FOREIGN KEY(EMPLOYEE) REFERENCES person_table(IDENTIFICATION))");
}
Screen of sqldatabse
Can someone help me?
Code of methods:
public boolean addDataToLocation(String Location){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COLL_2, Location);
long result = db.insert(TABLE_LOCATION, null, contentValues);
if(result == -1)
return false;
else
return true;
You appear to have two issues/misunderstandings.
The first is that specifying a foreign key doesn't automatically select a suitable value and update the column with such a value. Rather defining a foreign adds a constraint that says that the value must be a value that exists in the respective column of the parent table. If it does not then a conflict will occur.
As such you have to determine a suitable value (in your case an existing IDENTIFICATION value).
The second is that the SQLite provided with Android, by default does not have foreign key support turned on. Foreign key support can be turned on by either using
the foriegn_keys pragma to turn support on
or by using the SQliteDatabase method setForeignKeyConstraintsEnabled
noting that foreign key support cannot be turned on within a transaction. As such it is advisable to turn foreign key support on as soon as possible.
If using as sub class of SQLiteOpenHelper then it is suggested to override the onConfigure method and use the setForeignKeyConstraintsEnabled method.
I'm Using OID as a primary key with auto increment, but I want to make Txn No also auto increment. Is there any way to make it auto increment? I tried to use loop, but it seems doesn't work.
When I click the "Save" one time, Next time should be Txn No "2", but I can't think of it, because I used OID to Auto increment, so Txn No can't use it.
Here is My Code:
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "Person.db";
public static final String TABLE_NAME = "Person_Table";
public static final String COL_1 = "OID";
public static final String COL_2 = "TxnNo";
public static final String COL_3 = "Name";
public static final String COL_4 = "Amount";
public static final String COL_5 = "Date";
public static final String COL_6 = "Description";
public static final String COL_7 = "Description2";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_NAME + " (OID INTEGER PRIMARY KEY AUTOINCREMENT," +
"TxnNo TEXT, Name TEXT, Amount INTEGER,Date TEXT, Description TEXT,Description2 TEXT)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
public boolean insertData(String TxnNo, String Name, String Amount, String Date, String Description, String Description2) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COL_2, TxnNo);
contentValues.put(COL_3, Name);
contentValues.put(COL_4, Amount);
contentValues.put(COL_5, Date);
contentValues.put(COL_6, Description);
contentValues.put(COL_7, Description2);
long result = db.insert(TABLE_NAME, null, contentValues);
if (result == -1)
return false;
else
return true;
}
}
First thing with SQLite AUTOINCREMENT doesn't actually increment the ID, using INTEGER PRIMARY KEY will result in much the same, other than when you've had 9223372036854775807 rows added. All AUTOINCREMENT does is enforce an increasing number (so when the largest rowid is reached an SQLITE FULL exception occurs), otherwise (without AUTOINCREMENT) free lower numbers can be allocated, thus potentially circumventing the SQLITE FULL exception.
In fact what INTEGER PRIMARY KEY (with or without AUTOINCREMENT) does is make the columnn alias of the rowid (a normally hidden column that is given a unique 64 bit signed integer).
One of the rules is that only a single column can have INTEGER PRIMARY KEY (or PRIMARY KEY) coded per table. Which is the issue that you are facing.
A Solution
A way to do what you wish is to utilise a TRIGGER that is triggered when a new row is inserted and use it to update the inserted row with a value that is suffixed with the OID. e.g.
CREATE TRIGGER IF NOT EXISTS increment_tax_number
AFTER INSERT ON Person_Table
BEGIN
UPDATE Person_Table SET TxnNo = 'Txn no '||new.OID WHERE OID = new.OID;
END;
INSERT INTO Person_Table VALUES(null,'not a valid tax number as yet','Fred',15000,'2018-01-01','blah','more blah');
INSERT INTO Person_Table VALUES(null,'not a valid tax number as yet','Bert',25000,'2018-03-04','blah','more blah');
SELECT * FROM Person_Table;
For a new table the above results in :-
This solution could be incorporated by using :-
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_NAME + " (OID INTEGER PRIMARY KEY AUTOINCREMENT," +
"TxnNo TEXT, Name TEXT, Amount INTEGER,Date TEXT, Description TEXT,Description2 TEXT)");
db.execsql("CREATE TRIGGER If NOT EXISTS increment_tax_number AFTER INSERT ON Person_Table
BEGIN
UPDATE Person_Table SET TxnNo = 'Txn no '||new.OID WHERE OID = new.OID;
END");
}
You would need to delete the App's data, uninstall the App or increase the version number (i.e. use super(context, DATABASE_NAME, null, 2)). Noting that you would lose any existing data. To not lose data would be more complicated.
A More efficient solution
Of course, there is also the option of just utilising the OID as it appears that you want the numeric part appended to Txn No, so there is no need to even have a column that is a waste. The Txn No 1, Txn No 2 etc can be generated when required.
e.g. The following will generate the Txn No purely from the OID column :-
SELECT Name, 'Txn No '||OID AS txn_no,Amount,Description,Description2 FROM Person_Table;
Resulting in :-
To incorporate this solution you don't need to do anything other than use suitable queries (although you may wish to do away with the TxnNo column)
More about AUTOINCREMENT
Using AUTOINCREMENT incurs overheads that are rarely required. The SQLite documentation includes :-
The AUTOINCREMENT keyword imposes extra CPU, memory, disk space, and
disk I/O overhead and should be avoided if not strictly needed. It is
usually not needed.
SQLite Autoincrement
The overheads are because when AUTOINCREMENT is used the algorithm used to determine the new rowid adds a second stage of getting the respective row from the sqlite_sequence table and then using the higher of this and the highest rowid in the table (without AUTOINCREMENT just the highest rowid in the table is used). So the overheads are having to maintain and access this additional table for every insert.
As such it would be more efficient to define your table with either :-
CREATE TABLE IF NOT EXISTS Person_Table (OID INTEGER PRIMARY KEY,TxnNo TEXT, Name TEXT, Amount INTEGER,Date TEXT, Description TEXT,Description2 TEXT);
If you decide to have the TxnNo column
or :-
CREATE TABLE IF NOT EXISTS Person_Table (OID INTEGER PRIMARY KEY, Name TEXT, Amount INTEGER,Date TEXT, Description TEXT,Description2 TEXT);
If using the derived Txn No (more efficient solution)
You can't have 2 AUTOINCREMENT variables in the table. But now you declere: TxnNo TEXT it's very strange.
You can look for these variants sql-auto-increment-several
It may be, Sqlite not providing autoincrement for two column.
So i have several ways
first of all you need to use "TxnNo" as INTEGER or LONG.
at the time while you insert new record get Max "TxnNo" and increase it by 1. It is possible only if your whole database is synced in local. if it's not fully synced then its may occur duplication .
Use "TxnNo" as LONG and set current time in milliseconds. this will give you unique number every time. no need to get max. I would like to prefer this way. cause i'm also using this way.
I am attempting to read from an SQLite database I have created containing information on UK universities.
The table has the following columns:
Institution
Rank_2017
Guardian_score100
Satisfied_with_course
Satisfied_with_teaching
Satisfied_with_feedback
Student_to_staff_ratio
Average_entry_tariff
Career_after_6_months
I have populated the table from a CSV file, and then attempted to call a getUni() method that will return the information in each of the columns, and use them to build a University object, however when I check the values of each member variable of University, the name and rank have been set appropriately, however every variable after that has also been set to the value of Rank_2017.
getUni() Method
public University getUni(String id)
{
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_UNIVERSITIES, COLUMNS, " Institution = ?",
new String[] { id }, null, null, null, null);
if(cursor != null){
cursor.moveToFirst();
}
System.out.println("###" + cursor.getCount() + "###");
University uni = new University();
if(cursor != null){
uni.setUni_name(cursor.getString(0));
uni.setRank(cursor.getString(1));
uni.setGuardianScore(cursor.getString(2));
uni.setCourseSatisfaction(cursor.getString(3));
uni.setTeachingSatisfaction(cursor.getString(4));
uni.setFeedbackSatisfaction(cursor.getString(5));
uni.setStudentStaffRatio(cursor.getString(6));
uni.setAverageEntryTariff(cursor.getString(7));
uni.setCareerAfterSixMonths(cursor.getString(8));
}
// return University
return uni;
}
After calling cursor.getColumnCount() i can see that it returns 10 columns as expected, however something isn't quite right.
For example, if I call University uni = getUni("Glasgow"); , it will assign both the University name, and rank_2017 correctly, however assign each member variable after that the same as rank_2017.
CSV row example:
Glasgow,26,70.8,89.3,91.6,67.3,14.5,478.4,78.5
Any help solving this issue would be hugely appreciated.
I suspect when you imported the CSV file, it didn't work correctly. Perhaps you didn't specify a separator, and SQLite created a table for you with only one column. Or it populated the table strangely, and your SQL adapter is "helping" in a surprising way. That could happen if for instance your CSV file had some whitespace.
I would use the SQLite shell to verify that the Glassgow row appears as expected in the database. That at least will let you distinguish between SQLite issues and Java library issues (if any).
HTH.
I'm having trouble with something that works in the Notepad example.
Here's the code from the NotepadCodeLab/Notepadv1Solution:
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.notes_row, c, from, to);
This code seems to work fine. But just to be clear, I ran the ADB
utility and run SQLite 3. I inspected the schema as follows:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE notes (_id integer primary key autoincrement, title text
not null, body text not null);
All seems good to me.
Now on to my application, which, as far as I can see, is basically the same with
a few minor changes. I've simplified and simplified my code, but the
problem persists.
String[] from = new String[] { "x" };
int[] to = new int[] { R.id.x };
SimpleCursorAdapter adapter = null;
try
{
adapter = new SimpleCursorAdapter(this, R.layout.circle_row, cursor, from, to);
}
catch (RuntimeException e)
{
Log.e("Circle", e.toString(), e);
}
When I run my application, I get a RuntimeException and the following prints
in LogCat from my Log.e() statement:
LogCat Message:
java.lang.IllegalArgumentException: column '_id' does not exist
So, back to SQLite 3 to see what's different about my schema:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE circles (_id integer primary key autoincrement, sequence
integer, radius real, x real, y real);
I don't see how I'm missing the '_id'.
What have I done wrong?
One thing that's different between my application and the Notepad example is
that I started by creating my application from scratch using the
Eclipse wizard while the sample application comes already put together. Is
there some sort of environmental change I need to make for a new application
to use a SQLite database?
I see, the documentation for CursorAdapter states:
The Cursor must include a column named _id or this class will not
work.
The SimpleCursorAdapter is a derived class, so it appears this statement applies. However, the statement is technically wrong and somewhat misleading to a newbie. The result set for the cursor must contain _id, not the cursor itself.
I'm sure this is clear to a DBA because that sort of shorthand documentation is clear to them, but for those newbies, being incomplete in the statement causes confusion. Cursors are like iterators or pointers, they contain nothing but a mechanism for transversing the data, they contain no columns themselves.
The Loaders documentation contains an example where it can be seen that the _id is included in the projection parameter.
static final String[] CONTACTS_SUMMARY_PROJECTION = new String[] {
Contacts._ID,
Contacts.DISPLAY_NAME,
Contacts.CONTACT_STATUS,
Contacts.CONTACT_PRESENCE,
Contacts.PHOTO_ID,
Contacts.LOOKUP_KEY,
};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// ...
return new CursorLoader(getActivity(), baseUri,
CONTACTS_SUMMARY_PROJECTION, select, null,
Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC");
}
This has been answered and I would like to make it more comprehensive here.
SimpleCursorAdapter requires that the Cursor's result set must include a column named exactly "_id". Don't haste to change schema if you didn't define the "_id" column in your table.
SQLite automatically added an hidden column called "rowid" for every table. All you need to do is that just select rowid explicitly and alias it as '_id' Ex.
SQLiteDatabase db = mHelper.getReadableDatabase();
Cursor cur = db.rawQuery( "select rowid _id,* from your_table", null);
Tim Wu's code really works...
If you are using db.query, then it would be like this...
db.query(TABLE_USER, new String[] {
"rowid _id",
FIELD_USERNAME,
},
FIELD_USERNAME + "=" + name,
null,
null,
null,
null);
Yes , I also change the SELECT string query to fix this issue.
String query = "SELECT t.*,t.id as _id FROM table t ";
What solved my issue with this error was that I had not included the _id column in my DB query. Adding that solved my problem.
This probably isn't relevant anymore, but I just hit the same problem today. Turns out column names are case sensitive. I had an _ID column, but Android expects an _id column.
If you read the docs on sqlite, creating any column of type INTEGER PRIMARY KEY will internally alias the ROWID, so it isn't worth the trouble of adding an alias in every SELECT, deviating from any common utilities that might take advantage of something like an enum of columns defining the table.
http://www.sqlite.org/autoinc.html
It is also more straightforward to use this as the ROWID instead of the AUTOINCREMENT option which can cause _ID can deviate from the ROWID. By tying _ID to ROWID it means that the primary key is returned from insert/insertOrThrow; if you are writing a ContentProvider you can use this key in the returned Uri.
Another way of dealing with the lack of an _id column in the table is to write a subclass of CursorWrapper which adds an _id column if necessary.
This has the advantage of not requiring any changes to tables or queries.
I have written such a class, and if it's of any interest it can be found at https://github.com/cmgharris/WithIdCursorWrapper