How can I check whether the column already has value?

Question

How can I check whether the column already has value? Can use cursor to find?

I have two tables, one is table info and another is table workDetails

Table Info: ID(PK), Name, Weather, Date, Status, TimeIn_Info, TimeOut_Info

Table WorkDetails: ID(PK),Project,WorkDescription,Per,TimeIn,TimeOut // 4 row

There are 4 row in my WorkDetails and I only want the row which has value only will be inserted. And for the TimeOut_Info, it will get from TimeOutwhich is in table WorkDetails. If row 4 is empty, it will goes for row 3. If there exits a TimeOut value in row 3, it will insert into table Info and will not look for row 2 and row 1....

 public void checkRow2(String a, String b, String c, String d) {
       if ((TextUtils.isEmpty(a)) && (TextUtils.isEmpty(b)) && (TextUtils.isEmpty(c)) && (TextUtils.isEmpty(d))) {
          // Toast.makeText(getApplicationContext(), "Doss", Toast.LENGTH_LONG).show();
           Toast.makeText(getApplicationContext(), "Row 2 is empty", Toast.LENGTH_LONG).show();
           return;

       }else if ((a != null && a.trim().length() > 0) && ((TextUtils.isEmpty(b)) && (c != null && c.trim().length() > 0) && (d != null && 

d.trim().length() > 0))) {
               WD.insertWorkDetails(a2, a, b, c, d);
               Cursor mCursor = database.rawQuery("SELECT TimeOut_Info FROM " + MyDatabaseHelper.TABLE_INFO + " WHERE " +
                       MyDatabaseHelper.TimeOut_Info + "= '" + d + "'", null);
 if (mCursor == null) {
               database = dbHelper.getWritableDatabase();
               ContentValues values = new ContentValues();
               values.put(MyDatabaseHelper.TimeOut_Info, d);
               database.insert(MyDatabaseHelper.TABLE_INFO, null, values);
               Toast.makeText(getApplicationContext(), "No Per2", Toast.LENGTH_LONG).show();
           }

The coding else-if path I attached doesn't work although it already meet the condition. I wonder is it the way to check whether the selected column already has a value?

 Cursor cur = databaseb.rawQuery("SELECT COlumn COUNT(*) FROM +MyDatabaseHelper.TABLE_INFO+ ", null);
        if (cur.getCount() > 0){
            //do nothing everything's as it should be
        }
        else{
//
}

I have tried another method, but still no luck :(

Answer 1

A bit difficult to figure out what you are trying to do, but if you for example have a User table, keyed by UserId, with an optional (nullable) UserDescription, and you want to check if a particular user has a description, the SQL to do so can be one of the following:

-- Return non-null value if user has description, null if not, or no record if user not found
SELECT UserDescription
  FROM User
 WHERE UserId = ?

-- Return 1 if user has description, 0 if not, or no record if user not found
SELECT CASE WHEN UserDescription IS NULL THEN 0 ELSE 1 END AS HasDescription
  FROM User
 WHERE UserId = ?

-- Return 1 if user has description, or no record if not or if user not found
SELECT 1
  FROM User
 WHERE UserId = ?
   AND UserDescription IS NOT NULL

-- Return 1 if user has description, or 0 if not or if user not found
SELECT COUNT(*)
  FROM User
 WHERE UserId = ?
   AND UserDescription IS NOT NULL

There are more ways to do it.