I have a table with 3 columns "ID", "NAME" & "STATUS". I would like to execute a query on my database where I can get only one entry of "ID" which is located at the top row. I have a working sql query,
"SELECT TOP 1 ID from SAMPLE_TABLE WHERE Status='PENDING' ORDER BY ID ASC;"
This is so far what I implemented in android,
// Getting pending items
public int pendingContact() {
SQLiteDatabase db = this.getWritableDatabase();
Cursor mCount = db.query(
TABLE_CONTACTS ,
new String[] { "id" } ,
"status = ?" ,
new String[] { "PENDING" } ,
null ,
null ,
null
);
mCount.moveToFirst();
int count = mCount.getInt(0);
mCount.close();
return count;
}
Al through it gives the desired output but I would like to know if there is any other way of doing this more efficiently.
You can use Limit
public Cursor query (String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit)
limit - Limits the number of rows returned by the query, formatted as LIMIT clause. Passing null denotes no LIMIT clause.
You can do this:
Cursor mCount = db.query(TABLE_CONTACTS, new String[] { "id" }, "status = ?", new String[] { "PENDING" }, null, null, "id ASC", "1");
This will keep you from acquiring more data than you need.
When you use ORDER BY, the database will read and sort all PENDING items before it can return the first one.
When using MIN, nothing but the smallest value must be stored temporarily:
SELECT MIN(id) FROM Contacts WHERE Status = 'PENDING'
In code:
Cursor mCount = db.rawQuery("SELECT MIN(id) FROM Contacts WHERE Status = ?",
new String[] { "PENDING" });
Related
I don't know what's wrong with my code I follow the rule but I get wrong result. I want to search db and find all rows data but I only get last row from sqlite. my code to search database is bellow:
public ArrayList<ArrayList<ContractSaveDataFromDB>> ActiveContractData(String phone, String numberId)
{
ArrayList<ContractSaveDataFromDB> UserData = new ArrayList<ContractSaveDataFromDB>();
ArrayList<ArrayList<ContractSaveDataFromDB>> SendUserData =
new ArrayList<ArrayList<ContractSaveDataFromDB>>();
SQLiteDatabase db = this.getReadableDatabase();
String whereClause = "phone = ? AND numberId = ?";
String[] whereArgs = new String[]{
phone,
numberId
};
String orderBy = "activeContract";
Cursor res2=db.query("usersAccount",null,whereClause,whereArgs,null,null,orderBy);
res2.moveToFirst();
do{
UserData.clear();
int index;
ContractSaveDataFromDB contractSaveDataFromDB=new ContractSaveDataFromDB();
index = res2.getColumnIndex("buyAmount");
String buyAmount = res2.getString(index);
contractSaveDataFromDB.setBuyAmount(buyAmount);
UserData.add(contractSaveDataFromDB);
SendUserData.add(UserData);
} while(res2.moveToNext());
res2.close();
db.close();
return SendUserData;
I don't know what's wrong. I appreciate if you help me to solve my problem.
you already added where clause so maybe it is filtering your results try to remove it by change this
Cursor res2=db.query("usersAccount",null,whereClause,whereArgs,null,null,orderBy);
to this
Cursor res2=db.query("usersAccount",null,null,null,null,null,orderBy);
I believe that your issues is that you are trying to use an ArrayList of ArrayList of ContractSaveDataFromDB objects.
I believe that an ArrayList of ContractSaveDataFromDB objects would suffice.
It would also help you if you learnt to do a bit of basic debugging, as an issue could be that you are not extracting multiple rows.
The following is an alternative method that :-
uses the ArrayList of ContractSaveDataFromDB objects,
introduces some debugging by the way of writing some potentially useful information to the log
and is more sound, as it will not crash if no rows are extracted
i.e. if you use moveToFirst and don't check the result (false means the move could not be accomplished) then you would get an error because you are trying to read row -1 (before the first row) as no rows exists in the cursor.
:-
public ArrayList<ContractSaveDataFromDB> ActiveContractData(String phone, String numberId) {
ArrayList<ContractSaveDataFromDB> SendUserData = new ArrayList<ContractSaveDataFromDB>();
SQLiteDatabase db = this.getReadableDatabase();
String whereClause = "phone = ? AND numberId = ?";
String[] whereArgs = new String[]{
phone,
numberId
};
String orderBy = "activeContract";
Cursor res2 = db.query("usersAccount", null, whereClause, whereArgs, null, null, orderBy);
Log.d("RES2 COUNT", "Number of rows in Res2 Cursor is " + String.valueOf(res2.getCount()));
while (res2.moveToNext()) {
ContractSaveDataFromDB current_user_data = new ContractSaveDataFromDB();
current_user_data.setBuyAmount(res2.getString(res2.getColumnIndex("buyAmount")));
Log.d("NEWROW", "Adding data from row " + String.valueOf(res2.getPosition()));
SendUserData.add(current_user_data);
}
res2.close();
db.close();
Log.d("EXTRACTED", "The number of rows from which data was extracted was " + String.valueOf(SendUserData.size()));
return SendUserData;
}
If after running you check the log you should see :-
A line detailing how many rows were extracted from the table
A line for each row (if any were extracted) saying Adding data from row ? (where ? will be the row 0 being the first)
A line saying The number of rows from which data was extracted was ? (? will be the number of elements in the array to be returned)
I'm working on an small android app that maintains a small database of tools which I lend out to other people.
As part of the app, I am incorporating an sqllite database, where I am having a bit of trouble performing queries and working with cursors once the queries have been executed.
The code in question is as follows:
String COLUMN_NAME = "toolName";
String[] columns = { COLUMN_NAME };
String selection = COLUMN_NAME + " =?";
String[] selectionArgs = {tool};
Cursor cursor = mToolDb.query(ToolStatisticContract.ToolStatisticEntry.TABLE_NAME, columns,
selection, selectionArgs, null, null, null, null);
return Integer.parseInt(cursor.getString(3));
The contract for the database is as follows:
public class ToolStatisticContract {
public static final class ToolStatisticEntry implements BaseColumns {
public static final String TABLE_NAME = "tooltable";
public static final String COLUMN_TOOL_NAME = "toolName";
public static final String COLUMN_LIFESPAN = "lifespan";
public static final String COLUMN_USAGE = "usageTime";
}
}
I am essentially trying to extract out the value from COLUMN_USAGE, which seems to be producing errors with regards to parsing the value to an integer. The value in the COLUMN is actually an integer typecasted as a String from a previous segment of code, so I'm fairly certain the error is encompasssed with the code snippets above.
Thanks again in advance for all your help!
The code in question is as follows
The net SQL statement is something like:
SELECT toolName FROM tooltable WHERE toolName = ?
And there is no column with index 3, since you are only returning 1 column.
You need to:
Have usageTime in your column list (COLUMNS)
Move the Cursor to a valid row (as it initially is positioned before the first row)
Pass getInteger() the value that lines up with COLUMNS to retrieve usageTime
You could use the following. This uses null instead of columns, which will get all columns (i.e. resolves to SELECT * FROM table). It checks that a row has been returned and only then does it try to get the data. It also closes the cursor (you should close a cursor when done with it). It uses cursor.getInt() to get the integer value rather than convert it from a string to int. It assumes that you'll only get 1 row (if no rows then 0 will be returned).
int returnvalue = 0;
String COLUMN_NAME = "toolName";
String[] columns = { COLUMN_NAME };
String selection = COLUMN_NAME + " =?";
String[] selectionArgs = {tool};
Cursor cursor = mToolDb.query(ToolStatisticContract.ToolStatisticEntry.TABLE_NAME, null,
selection, selectionArgs, null, null, null, null);
if (cursor.getCount() > 0) {
cursor.moveToFirst();
returnvalue = cursor.getInt(2);
//or returnvalue = Integer.parseInt(cursor.getString(2));
}
cursor.close();
return returnvalue;
Note! I haven't checked this just coded it from memory, so apologies for the odd mistake.
To do the above using specific columns then you could use:-
String COLUMN_NAME = "toolName";
String[] columns = { COLUMN_USAGE };
String selection = COLUMN_NAME + " =?";
String[] selectionArgs = {tool};
Cursor cursor = mToolDb.query(ToolStatisticContract.ToolStatisticEntry.TABLE_NAME, columns,
selection, selectionArgs, null, null, null, null);
In which case the column index would be 0 (that is the index is according to the column's in the cursor). However it might be better to use, the following which gets the column index according to the column's name:-
cursor.getInt(cursor.getColumnIndex(COLUMN_USAGE);
The easiest way to read a single value from the database is to use a helper function that allows you to avoid having to handle cursor objects:
String query = "SELECT usageTime FROM tooltable WHERE toolName = ?";
String[] selectionArgs = { tool };
long returnvalue = DatabaseUtils.longForQuery(mToolDb, query, selectionArgs);
i want to filter multiple data such as
id = "1,3,5" from columnid which is having 1 to 10 id
and another column such as name
name = "a,e,d" from name column of 10 records
and another criteria such as age
age = "21,23,20" from age column of 10 records from same table,
one example i got is
Cursor cursor = db.query("TABLE_NAME",new String[]{"ColumnName"}, "ColumnName=?",new String[]{"value"}, null, null, null);
which is just for one column but i want to get data from multiple column, can anyone help me?
try this working example,
Cursor cursor =
db.query(TABLE_DIARYENTRIES,
new String[] {},
STUDENT_ID + " IN ("+resultStudent+")"+ " AND " +CLASS_NAME + " IN ("+resultClass+")"
+ " AND " +SUBJECT_NAME + " IN ("+resultSubject+")"
null, null, null, null);
and your result string should be 'a','b','c'
I really like the way Google's example is structured. Because for noobies such as myself it makes it really clear what I am doing. And it is also more robust to SQL injections. Here is my modified version of the Google example:
//Column(s) I want returned
String[] projection = {"ColumnIWantReturned"};
//Column(s) I want to filer on
String selection = "FilterColumn1 IN (?) and FilterColumn2 IN (?, ?)";
String[] selectionArgs = {"ArgumentForFilterColumn1", "FirstArgumentForFilterColumn2", "SecondArgumentForFilterColumn2"};
Cursor cursor = db.query(
"MyTable", // The table to query
projection, // The array of columns to return (pass null to get all)
selection, // The columns for the WHERE clause
selectionArgs, // The values for the WHERE clause
null, // don't group the rows
null, // don't filter by row groups
null // The sort order
);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
Log.d("this-is-a-test", cursor.getString(0));
cursor.moveToNext();
}
cursor.close();
I have database which contains "date" column and "item" column.
I want that user could update specific row in the database.
I trying to do it with update method in SQLiteDatabase class.
My problem is that i dont know how to make update method find exactly the row i want.
I saw some example that use it with parameters from one word.
like this:
ourDatabase.update(tableName, cvUpdate, rowId + "=" + item , null);
My problem is that i want to update the row that have specific item and date. so the name of the item alone is not enough.
I tried this code below but its didnt work, hope youll can help me.
public void updateEntry(String item, String date) throws SQLException{
String[] columns = new String[]{myItem, myDate};
Cursor c = ourDatabase.query(tableName, columns, null, null, null, null, null);
long position;
ContentValues cvUpdate = new ContentValues();
cvUpdate.put(date, myDate);
cvUpdate.put(item, myExercise);
int itemAll = c.getColumnIndex(myItem);
int dateAll = c.getColumnIndex(myDate);
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
if (c.getString(itemAll).equals(myItem) && c.getString(dateAll).equals(myDate))
{
position = c.getPosition();
break;
}
}
ourDatabase.update(tableName, cvUpdate, rowId + "=" + position , null);
}
First, the columns String[] is supposed to contain column names, such as "_ID", or whatever are the column names you have used. Given that you compare the content of the column myItem with the object myItem, I assume there is a confusion somewhere here.
Secondly, rowId and position are different things in SQL, especially if you delete rows, as the row id usually is autoincrement, and especially since your query is not explicitely sorted. Replacing c.getPosition() by c.getLong(c.getColumnIndex(ID_COLUMN)) would make more sense.
Thirdly, sql is nice because you can query it. For example, rather than get all items and loop to find the matching date and item, you can :
String whereClause = ITEM_COLUMN + " = ? and " + DATE_COLUMN + " = ?";
String[] whereArgs = new String[] { item, date };
Cursor c = ourDatabase.query(tableName, columns, whereClause, whereArgs, null, null, null);
instead of your for loop.
Forthly, you can even make the query in the update :
String whereClause = ITEM_COLUMN + " = ? and " + DATE_COLUMN + " = ?";
String[] whereArgs = new String[] { item, date };
ourDatabase.update(tableName, cvUpdate, whereClause, whereArgs);
Extra tip: use full caps variable names for contants such as column names, it help with readability.
In my project I have to select multiple values and pass it to a query. i.e page1 contains checkboxes. I am storing the selected checkbox id's into an array.
I am shuffling that array and getting the values randomly. Now I need to pass these random values to a query. Using IN operator in database I can pass the values
statically but how can I pass the values dynamcially to the query.
For ex:(Passing values statically)
SELECT * FROM Persons WHERE person_id IN ('21','22')
In the above query the id's 21 and 22 are know previously and so we are passing statically but I want to send the values to query dynamically.
Page1:
public static ArrayList<String> chksublist = new ArrayList<String>();
Page2:
Collections.shuffle(chksublist );
SELECT * FROM Persons WHERE person_id IN ('21','22')
In the above line I want to send the random values which are in chksublist array.
String query = "SELECT * FROM Persons WHERE person_id IN (" + TextUtils.join(",", chksublist) + ")";
But shuffling the chksublist before sending it to your SQL query has no impact on the result set you get from SQL. It will not randomly permute your results. Remove Collections.shuffle(chksublist); and use
String query = "SELECT * FROM Persons WHERE person_id IN (" + TextUtils.join(",", chksublist) + ") ORDER BY RANDOM()";
see how values are dynamicaly passed
// Getting single contact
public Contact getContact(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
// here new String[] { String.valueOf(id) } value is added dynamicaly which is passed to the function
if (cursor != null)
cursor.moveToFirst();
Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
cursor.getString(1), cursor.getString(2));
// return contact
return contact;
}
You can generate your query like this
int values[]; //it contains your generated values like 21,22....
String query="SELECT * FROM Persons WHERE person_id IN (";
for(int i=0;i<values.length;i++){
query=query+"'"+values[i]+"'";
if(i<values.length-1){
query=query+","; //No , after last values
}
}
query+=")";
finally pass this query.
Try it
cursor = database.query(tablename,
new String[] {"TopName"}, "id IN(?,?)", new String[]{"2","3"}, null, null, null);
using raw query
String query = "SELECT * FROM Persons WHERE person_id IN ("+parameter1+","+parameter2+")";
db.rawQuery(query);