We pass so many parameters to query() method of android. Android has simplified our work by giving query method. Is there any way so that i can print the sql query which android will form from this query method arguments which android creates and sends to sqlite.
According to a previous post, I have tried and I got the following solution in order to print the query string in the log.
Use buildQueryString method of SQLiteQueryBuilder. It takes almost same parameters as query() method takes .........
String sqlQry = SQLiteQueryBuilder.buildQueryString(false,TABLE_NAME, null, COLUMN_NAME_PATIENTID +"="+ patientID, null, null, COLUMN_NAME_PATIENTFIRSTNAME, null);
Log.i(TAG, sqlQry);
cursor = db.query(TABLE_NAME, null, COLUMN_NAME_PATIENTID +"="+ patientID, null, null, null, COLUMN_NAME_PATIENTFIRSTNAME);
For what it's worth, if you run under the debugger you can view the private member variable mQuery, which shows you the exact SQL query executed on that cursor - it's handy and can be used on demand without mucking with any code.
Since the query methods are of cursor type, I am not sure whether It will be printed or not.
If you want to debug any query, you can use EXPLAIN QUERY PLAN keyword along with the query or use SQLiteQueryBuilder() or simply run the SQL query by using rawQuery() method.
You can take references from:
http://developer.android.com/reference/android/database/sqlite/SQLiteQueryBuilder.html
http://www.sqlite.org/eqp.html
Related
I had a problem with updating of a column's value at a particular row. I had written
Cursor c = mDb.rawQuery("UPDATE "+book+" SET footnotes='" + note + "' WHERE chapter="+chapter+" and verse="+verse+"", null);
c.close();
But on adding c.moveToFirst() it worked. Why is that?
Cursor c = mDb.rawQuery("UPDATE "+book+" SET footnotes='" + note + "' WHERE chapter="+chapter+" and verse="+verse+"", null);
c.moveToFirst();
c.close();
Why is c.moveToFirst() necessary here, any particular reason?
There is an explation for c.moveToFirst()
(What is The use of moveToFirst () in SQLite Cursors) which briefly suggests that using c.moveToFirst() does two things
allows you to test whether the query returned an empty set
moves the cursor to the first result
But how does the above two things help in updation?
Think of rawQuery() as a wrapper for the C library sqlite3_prepare_v2() that compiles the SQL but does not run it, while think of moveTo..() as a wrapper for sqlite3_step() that is required for actually executing the prepared statement.
Related: What is the correct way to do inserts/updates/deletes in Android SQLiteDatabase using a query string?
I wrote a select query to access set of records from database by setting null for the argument 'orderBy' in the query(). I found that order of records returned by query() method when I run the application in mobile is completely different when I run the same sample application in tablet.
My Query:
Cursor cursor = database.query(true, tableName, downloadQueueTableColumnNames, selection, null, null, null, null, null);
Here, in the query orderBy field is null.
I hope someone to explain the reason behind this...
If you aren't ordering the results, they can be returned in any order. The same device doesn't have to give the same order if you call it twice in a row. If you want it in the same order every time, you must use an order by.
Hi I cant get unique rows tried this from the documentation:
public Cursor getcepaUnico(){
return database.query(true, "vino", new String[] {"_id", "cepa"}, null, null, null, null, "cepa", null);}
but shows duplicated rows even if the DISTINCT boolean is changed.
Also tried this:
public Cursor getCepaUnico() {
return database.rawQuery("select DISTINCT cepa from vinos", null);}
And the app crash after calling the method.
Setting distinct to true should have returned distinct results. Is it possible that your code which loops through the cursor is incorrect? You might want to post that also for review.
Regarding your rawQuery, you are using a different table name which is probably what is causing the crash. It should be "select DISTINCT cepa from vino" (not vinos) to match your query statement.
Not sure if this will solve your problem, but sometimes I just pull the db from the emulator (in the DDMS view in Eclipse) and run the query directly using an sqlite editor when my raw queries don't work; if the query shows what you want in the editor then use the query in the rawQuery method.
Firefox has a good sqlite editor.
I am trying to get call log by using the CallLog.Calls content provider. However, I am little lost about the query I need to make. I am able to make a query and load the result in a ListView. But the query return all types of call.
Of course I can use a switch-case and take appropriate action as per the types of call returned. But for my program I only need the outgoing call logs.
So, how do I modify the query to get only outgoing call types. (I believe I have to use CallLog.Calls.OUTGOING_TYPE somewhere?). I have tried to modify the query in various ways but I keep getting error. If I try to supply the CallLog.Calls.OUTGOING_TYPE as an selection arg I get an error as its an int type and the query looks for String type.
I may be missing something simple, but can't figure it out. Any help would be much appreciated. Thank You. Here's my query below,
getContentResolver().query(CallLog.Calls.CONTENT_URI,null, null, null, ORDER_BY );
Try this code snippet:
Cursor c = getContentResolver().query(CallLog.Calls.CONTENT_URI, null,
CallLog.Calls.TYPE + "=?",
new String[] { String.valueOf(CallLog.Calls.OUTGOING_TYPE) },
ORDER_BY);
Android's API provides a clean mechanism via SQLite to make queries into the contact list. However, I am not sure how to limit the results:
Cursor cur = ((Activity)mCtx).managedQuery(
People.CONTENT_URI,
columns,
"LIMIT ? OFFSET ?",
new String[] { Integer.toString(limit), Integer.toString(offset) },
null
);
Doesn't work.
Actually, depending on the provider you can append a limit to the URI as follows:
uri.buildUpon().appendQueryParameter("limit", "40").build()
I know the MediaProvider handles this and from looking at recent code it seems you can do it with contacts too.
You are accessing a ContentProvider, not SQLite, when you query the Contacts ContentProvider. The ContentProvider interface does not support a LIMIT clause directly.
If you are directly accessing a SQLite database of your own, use the rawQuery() method on SQLiteDatabase and add a LIMIT clause.
I found out from this bug that Android uses the following regex to parse the LIMIT clause of a query:
From <framework/base/core/java/android/database/sqlite/SQLiteQueryBuilder.java>
LIMIT clause is checked with following sLimitPattern.
private static final Pattern sLimitPattern = Pattern.compile("\\s*\\d+\\s*(,\\s*\\d+\\s*)?");
Note that the regex does accept the format offsetNumber,limitNumber even though it doesn't accept the OFFSET statement directly.
I think you have to do this sort of manually. The Cursor object that is returned from the managedQuery call doesn't execute a full query right off. You have to use the Cursor.move*() methods to jump around the result set.
If you want to limit it, then create your own limit while looping through the results. If you need paging, then you can use the Cursor.moveToPosition(startIndex) and start reading from there.
You can specify the "limit" parameter in the "order" parameter, maybe even inside other parameters if you don't want to sort, because you'll have to specify a column to sort by then:
mContentResolver.query(uri, columnNames, null, null, "id LIMIT 1");