my question seems silly but it makes me headache by below code. Below code print contactId and telephone number to Screen.
It works well, but something I need to know more clearer:
ContentResolver solver = getContentResolver();
String mess="";
Cursor cursor = solver.query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null);
while (cursor.moveToNext()){
String contactId = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts._ID));
mess = mess + "ID: "+contactId+"\n";
Cursor phones = getContentResolver().query( ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, ContactsContract.CommonDataKinds.Phone.CONTACT_ID +" = "+ contactId, null, null);
while (phones.moveToNext()) {
String phoneNumber = phones.getString(phones.getColumnIndex( ContactsContract.CommonDataKinds.Phone.NUMBER));
mess = mess + phoneNumber + "\n";
}
}
The thing I don't know is this line of above code:
Cursor phones = getContentResolver().query( ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, ContactsContract.CommonDataKinds.Phone.CONTACT_ID +" = "+ contactId, null, null);
As in Android Development about third parameter:
selection : A filter declaring which rows to return, formatted as an
SQL WHERE clause (excluding the WHERE itself). Passing null will
return all rows for the given URI.
So, as this defination, CONTACT_ID acts as "A ROW". (because it filter which row to return),
but as this line, CONTACT_ID acts as "A COLUMN":
String contactId = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts._ID));
Please explain for me this point.
thanks :)
It's a column (declared like this INTEGER PRIMARY KEY AUTOINCREMENT). In:
Cursor phones = getContentResolver().query(
ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
null,
ContactsContract.CommonDataKinds.Phone.CONTACT_ID +" = "+ contactId,
null, null);
you query the ContentProvider but use the _ID column to filter the results. You are saying: "I want the rows from the ContentProvider where in the column _ID I find only the value contactId". In:
String contactId = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts._ID));
_ID is used to get the column index integer(to get the values from that column) so you don't have to use simple numbers like 0, 1, 2 and possible avoid mistakes.
Edit:
The second parameter(also referred as projection) represents the columns of data that you want to retrieve from the provider(null = get all columns). You could look at the second parameter as a filter, you only get those column that you specified in the array(for example maybe you don't want several columns because you will not use them, so for the second parameter you set a string array with the columns that you do want and omit the ones that you don't need). The third parameter filter the rows, the second parameter filter the columns you retrieved()
You should take a look of sql queries, if we want to select column column1 from table A, with filtering if its value is 5, then we would write this query as:
SELECT column1 From A WHERE column1=5
It means Selecting values from table with column1 value equal to 5. So nothing is unusual here.
CONTACT_ID is a column.
when you use "CONTACT_ID = 10" filter expression for example
you will get all the rows that have the value 10 in their CONTACT_ID cell.
see the following link about where clause in SQL :
http://www.w3schools.com/sql/sql_where.asp
Related
I am using the query method of SQLiteDatabase. How do I use the query method?
I tried this:
Cursor cursor = sqLiteDatabase.query(
tableName, tableColumns, whereClause, whereArgs, groupBy, having, orderBy);
tableColumns - columns parameter is constructed as follows.
String[] columns = new String[]{KEY_ID, KEY_CONTENT};
If we need to get all the fields, how should the column parameter to be constructed. Do we need to include all the Field Names in String array?
How do I properly use the query method?
tableColumns
null for all columns as in SELECT * FROM ...
new String[] { "column1", "column2", ... } for specific columns as in SELECT column1, column2 FROM ... - you can also put complex expressions here:
new String[] { "(SELECT max(column1) FROM table1) AS max" } would give you a column named max holding the max value of column1
whereClause
the part you put after WHERE without that keyword, e.g. "column1 > 5"
should include ? for things that are dynamic, e.g. "column1=?" -> see whereArgs
whereArgs
specify the content that fills each ? in whereClause in the order they appear
the others
just like whereClause the statement after the keyword or null if you don't use it.
Example
String[] tableColumns = new String[] {
"column1",
"(SELECT max(column1) FROM table2) AS max"
};
String whereClause = "column1 = ? OR column1 = ?";
String[] whereArgs = new String[] {
"value1",
"value2"
};
String orderBy = "column1";
Cursor c = sqLiteDatabase.query("table1", tableColumns, whereClause, whereArgs,
null, null, orderBy);
// since we have a named column we can do
int idx = c.getColumnIndex("max");
is equivalent to the following raw query
String queryString =
"SELECT column1, (SELECT max(column1) FROM table1) AS max FROM table1 " +
"WHERE column1 = ? OR column1 = ? ORDER BY column1";
sqLiteDatabase.rawQuery(queryString, whereArgs);
By using the Where/Bind -Args version you get automatically escaped values and you don't have to worry if input-data contains '.
Unsafe: String whereClause = "column1='" + value + "'";
Safe: String whereClause = "column1=?";
because if value contains a ' your statement either breaks and you get exceptions or does unintended things, for example value = "XYZ'; DROP TABLE table1;--" might even drop your table since the statement would become two statements and a comment:
SELECT * FROM table1 where column1='XYZ'; DROP TABLE table1;--'
using the args version XYZ'; DROP TABLE table1;-- would be escaped to 'XYZ''; DROP TABLE table1;--' and would only be treated as a value. Even if the ' is not intended to do bad things it is still quite common that people have it in their names or use it in texts, filenames, passwords etc. So always use the args version. (It is okay to build int and other primitives directly into whereClause though)
This is a more general answer meant to be a quick reference for future viewers.
Example
SQLiteDatabase db = helper.getReadableDatabase();
String table = "table2";
String[] columns = {"column1", "column3"};
String selection = "column3 =?";
String[] selectionArgs = {"apple"};
String groupBy = null;
String having = null;
String orderBy = "column3 DESC";
String limit = "10";
Cursor cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy, limit);
Explanation from the documentation
table String: The table name to compile the query against.
columns String: A list of which columns to return. Passing null will return all columns, which is discouraged to prevent reading data
from storage that isn't going to be used.
selection String: A filter declaring which rows to return, formatted as an SQL WHERE clause (excluding the WHERE itself). Passing
null will return all rows for the given table.
selectionArgs String: You may include ?s in selection, which will be replaced by the values from selectionArgs, in order that they
appear in the selection. The values will be bound as Strings.
groupBy String: A filter declaring how to group rows, formatted as an SQL GROUP BY clause (excluding the GROUP BY itself). Passing null
will cause the rows to not be grouped.
having String: A filter declare which row groups to include in the cursor, if row grouping is being used, formatted as an SQL HAVING
clause (excluding the HAVING itself). Passing null will cause all row
groups to be included, and is required when row grouping is not being
used.
orderBy String: How to order the rows, formatted as an SQL ORDER BY clause (excluding the ORDER BY itself). Passing null will use the
default sort order, which may be unordered.
limit String: Limits the number of rows returned by the query, formatted as LIMIT clause. Passing null denotes no LIMIT clause.
Where clause and args work together to form the WHERE statement of the SQL query. So say you looking to express
WHERE Column1 = 'value1' AND Column2 = 'value2'
Then your whereClause and whereArgs will be as follows
String whereClause = "Column1 =? AND Column2 =?";
String[] whereArgs = new String[]{"value1", "value2"};
If you want to select all table columns, i believe a null string passed to tableColumns will suffice.
if your SQL query is like this
SELECT col-1, col-2 FROM tableName WHERE col-1=apple,col-2=mango
GROUPBY col-3 HAVING Count(col-4) > 5 ORDERBY col-2 DESC LIMIT 15;
Then for query() method, we can do as:-
String table = "tableName";
String[] columns = {"col-1", "col-2"};
String selection = "col-1 =? AND col-2=?";
String[] selectionArgs = {"apple","mango"};
String groupBy =col-3;
String having =" COUNT(col-4) > 5";
String orderBy = "col-2 DESC";
String limit = "15";
query(tableName, columns, selection, selectionArgs, groupBy, having, orderBy, limit);
db.query(
TABLE_NAME,
new String[] { TABLE_ROW_ID, TABLE_ROW_ONE, TABLE_ROW_TWO },
TABLE_ROW_ID + "=" + rowID,
null, null, null, null, null
);
TABLE_ROW_ID + "=" + rowID, here = is the where clause. To select all values you will have to give all column names:
or you can use a raw query like this
db.rawQuery("SELECT * FROM permissions_table WHERE name = 'Comics' ", null);
and here is a good tutorial for database.
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();
public static final String KEY_HIGH
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
KEY_HIGH + " INTERGE);"
);
}
public long createEntry(String high) {
ContentValues cv = new ContentValues();
cv.put(KEY_HIGH, high);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
String[] columns = new String[]{KEY_HIGH,KEY_NAME};
Cursor c = ourDatabase.query(
DATABASE_TABLE,
columns, null, null, null, null, KEY_HIGH + " DESC");
I am trying to sort by the column KEY_HIGH, however, the result came out like this:
4
3
2
10
11
1
How do I sort them as numbers from highest to lowest?
thanks.
From the Android docs:
public Cursor query (String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
Added in API level 1
Query the given table, returning a Cursor over the result set.
Parameters
table The table name to compile the query against.
columns A list of which columns to return. Passing null will return all columns, which is discouraged to prevent reading data from storage that isn't going to be used.
selection A filter declaring which rows to return, formatted as an SQL WHERE clause (excluding the WHERE itself). Passing null will return all rows for the given table.
selectionArgs You may include ?s in selection, which will be replaced by the values from selectionArgs, in order that they appear in the selection. The values will be bound as Strings.
groupBy A filter declaring how to group rows, formatted as an SQL GROUP BY clause (excluding the GROUP BY itself). Passing null will cause the rows to not be grouped.
having A filter declare which row groups to include in the cursor, if row grouping is being used, formatted as an SQL HAVING clause (excluding the HAVING itself). Passing null will cause all row groups to be included, and is required when row grouping is not being used.
orderBy How to order the rows, formatted as an SQL ORDER BY clause (excluding the ORDER BY itself). Passing null will use the default sort order, which may be unordered.
Returns
A Cursor object, which is positioned before the first entry. Note that Cursors are not synchronized, see the documentation for more details.
See Also
Cursor
Note that the final is named orderBy. This is where you can specify which column (or columns) to sort on. Also note that you do not need to include the "ORDER BY" keywords that you would use in a SQL statement.
I was having the same problem.It has a very simple solution:
In your CREATE_TABLE statement do this: " INTEGER, "+KEY_HIGH+ //your remaining things.
no need for the comma after the last null
Cursor c = ourDatabase.query(
DATABASE_TABLE,
columns, null, null, null, null + " ORDER BY " + KEY_HIGH + " DESC");
I'm trying to use the implementation of the code found in this question post: How to read contacts on Android 2.0 but I can't figure out how to get it also run through the given, family, or display name columns. How can I get this implementation (the large one in the linked question) to give me the given and display names of the contacts as it loops through each row? I want to use this implementation specifically because it loops through the specified columns in each row and returns the information in the order it is in the row.
Here is the implementation from the other question that I'm referring to:\
Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI,null, null, null, null);
while (cursor.moveToNext()) {
String contactId = cursor.getString(cursor.getColumnIndex(
ContactsContract.Contacts._ID));
String hasPhone = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER));
if (Boolean.parseBoolean(hasPhone)) {
// You know it has a number so now query it like this
Cursor phones = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, ContactsContract.CommonDataKinds.Phone.CONTACT_ID +" = "+ contactId, null, null);
while (phones.moveToNext()) {
String phoneNumber = phones.getString(phones.getColumnIndex( ContactsContract.CommonDataKinds.Phone.NUMBER));
}
phones.close();
}
Cursor emails = getContentResolver().query(ContactsContract.CommonDataKinds.Email.CONTENT_URI, null, ContactsContract.CommonDataKinds.Email.CONTACT_ID + " = " + contactId, null, null);
while (emails.moveToNext()) {
// This would allow you get several email addresses
String emailAddress = emails.getString(
emails.getColumnIndex(ContactsContract.CommonDataKinds.Email.DATA));
}
emails.close();
}
cursor.close();
First of all, the answer in the linked post is a bit obsolete, because there now is documentation for Contacts Provider at developer.android.com.
Second, the problem you're having is that you're querying the "data" table with a contact ID for the contacts table, and that won't work.
The Contacts Provider is a three-tiered arrangement of tables. The top level is the Contacts table, whose constants are defined in ContactsContract.Contacts. One of its columns is
ContactsContract.Contacts._ID, which identifies a contact row. HOWEVER, a row in this table is an aggregation of individual contacts from various sources.
The individual contacts are stored in ContactsContract.RawContacts. For each ContactsContract.Contacts._ID, there can be more than one row in ContactsContract.RawContacts.
For each row in ContactsContract.RawContacts, there are one or more rows in ContactsContract.Data. Each row has a MIME type that tells you what type of data it is. For example, a row in ContactsContract.RawContacts can have three rows in ContactsContract.Data that have the MIME type for phone numbers. Each of the three "data" rows is a different type of phone number (home, mobile, work) for the contact in ContactsContract.RawContacts.
You can see why looking for ContactsContract.Contacts._ID in ContactsContract.Data won't work; that's the wrong ID to look for.
Rather than re-write the documentation here, I suggest you take a look at it. It has some nice illustrations that help explain what I'm getting at:
Contacts Provider
I am using the query method of SQLiteDatabase. I need help with the orderBy parameter of this method.
Cursor cursor = sqLiteDatabase.query(tableName, tableColumns, whereClause, whereArgs, groupBy, having, orderBy);
public Cursor getAllCustomexp(int TID) throws SQLException
{
Cursor mCursor =
db.query(false, CEXP_TABLE, new String[] {KEY_CEID, FLD_CETID, FLD_CEEID, FLD_CEMID,
FLD_CEAMT, FLD_CESEL}, FLD_CETID + " = " + TID, null,
null, null, FLD_CEEID, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
Question 1:
In the above query the result set will be sorted by FLD_CEEID in ascending or descending order ?
Question 2:
If I need to order the result set first by FLD_CEEID and then by FLD_CEMID how should i construct the order by parameter of this query.
Is it possible to do multiple order by using this method?
From SQLite docs:
If a SELECT statement that returns more than one row does not have an
ORDER BY clause, the order in which the rows are returned is
undefined. Or, if a SELECT statement does have an ORDER BY clause,
then the list of expressions attached to the ORDER BY determine the
order in which rows are returned to the user. Rows are first sorted
based on the results of evaluating the left-most expression in the
ORDER BY list, then ties are broken by evaluating the second left-most
expression and so on. The order in which two rows for which all ORDER
BY expressions evaluate to equal values are returned is undefined.
Each ORDER BY expression may be optionally followed by one of the
keywords ASC (smaller values are returned first) or DESC (larger
values are returned first). If neither ASC or DESC are specified, rows
are sorted in ascending (smaller values first) order by default.
Answer 1: Result set will be sorted in ascending order.
Answer 2:
String orderBy = FLD_CEEID + " ASC, " + FLD_CEMID + " ASC";
db.query(false, CEXP_TABLE, new String[] {KEY_CEID, FLD_CETID, FLD_CEEID, FLD_CEMID,
FLD_CEAMT, FLD_CESEL}, FLD_CETID + " = " + TID, null,
null, null, orderBy, null);
It works like in SQL Select Order By. You can find details here: http://en.wikipedia.org/wiki/Order_by_(SQL) .