sqlite rawquery无法正常工作

Question

I have two table their names are profile and messages. I try to get profile data and last message which related by profileId from sql.

profiles

• profileId(INTEGER)
• profileName(TEXT)
• profileImgPath(TEXT)

messages

• messageId (INTEGER)
• profileId (INTEGER)
• messageContent (INTEGER)
• messageType (INTEGER)
• messageStatus(INTEGER)
• messageTime(TEXT)

data examples

my query

SQLiteDatabase db = this.getReadableDatabase();


     String selectQuery = "select " +
     "profiles.profileId," +
     "profiles.profileName," +
     "profiles.profileImgPath," +
     "profiles.profileStatus," +
     "messages.messageContent," +
     "messages.messageTime " +
     "from profiles left join messages on profiles.profileId=messages.profileId " +
     "group by profiles.profileId " +
     "order by messages.messageId DESC;";
          Cursor c = db.rawQuery(selectQuery, null);
    Log.i("query",selectQuery);
    if (c.moveToFirst()) {
        do {

            Log.i("gokberksql", c.getString(1) + "x" + c.getString(4));
            } while (c.moveToNext());
    }

results

gokberksql﹕ sinanxKanka naber

But need to return

gokberksql﹕ sinanxIyi senden naber

In addition this query working well in my computer editors but android results not correctly.

Answer 1

You should select the max messageTime in your query. This will give you the values of columns in the same row as the one that contains the max.

String selectQuery = "select " +
    "profiles.profileId," +
    "profiles.profileName," +
    "profiles.profileImgPath," +
    "profiles.profileStatus," +
    "messages.messageContent," +
    "max(messages.messageTime) as messageTime " + // <- here
    "from profiles " +
    "left join messages on profiles.profileId = messages.profileId " +
    "group by profiles.profileId" +
    "order by profiles.profileId, messages.messageId DESC;";

Note that this behavior was introduced in SQLite version 3.7.11, which became standard in API 16 (JellyBean). If you need to support API 15 or older, you may have to use a different query.

Answer 2

Why do you have a group by profiles.profileId, that is not needed in your case since you are not doing any aggregations over the profileId group. Try with

String selectQuery = "select " +
   "profiles.profileId," +
   "profiles.profileName," +
   "profiles.profileImgPath," +
   "profiles.profileStatus," +
   "messages.messageContent," +
   "messages.messageTime " +
 "from profiles left join messages on   profiles.profileId=messages.profileId " +
   "order by profiles.profileId, messages.messageId DESC;";