当表2的某些行更新时，Sqlite触发器将更新表1

Question

I have two tables in sqlite in android:

Table1: Outlets

id    pid   OutletName   Status
1      1    Tesco         1
2      1    Coors         1
3      2    Coors         1

Table2: projectparams

ppid projectname outletname  param          projStatus
1      RA_Pepsi   Tesco       shelfstrip       2
2      RA_Pepsi   Tesco       shelfleft        2
3      RA_Cocola  Coors       shelfstrip       1

Table1: For every PID (ProjectID) there are multiple Outlets stored in OutletName.

Table2: For each outlet there are multiple params stored in project params.

Whenever the user completes a task the param in Table2 is updated to 2. In the above example, when the user completes two tasks in Tesco, the status would be updated to 2 upon completion.

I am trying to set the outlets status to 2 based on completion of tasks for every outlet. In this example, when the status is updated to 2 in projectparam table, I want the Status in Outlets to be updated to 2 for the outlet Tesco.

I am using the following codes:

triggered when the task gets completed.

private void updateTaskStatus() {
        SQLiteDatabase db = sqLiteHelper.getWritableDatabase();
        String spinTextRecovered = spnTxt.getString("spinText", null);
        String updateTable = "update projectparams set projStatus=2 where param='"+spinTextRecovered+"' and projectName='"+projectName+"' and OutletName='"+outletName+"'";
        db.execSQL(updateTable);
        takePicButton.setEnabled( false );
    }

Triggered every time when the task gets completed and updates the outlet status when all the tasks for an outlet is completed.

   private void updateOutletStatus() {
        String query = "select OutletName from projectparams where projectName= '"+projectName+"' and OutletName= '"+outletName+"' group by projStatus";
        if (sqLiteHelper.getData(query).getCount()==1) {
            Toast.makeText( getApplicationContext(), "No more tasks in this outlet!", Toast.LENGTH_SHORT ).show();
            SQLiteDatabase db = sqLiteHelper.getWritableDatabase();
            String outletUpdate = "update outlets set Status=2 where OutletName='"+outletName+"' and pid = (select id from projects where ProjectName = '"+projectName+"' ) ";
            db.execSQL(outletUpdate);
        }
    }

The above code works...however since I am using an intent to display the projects, outlets and task parameters, many times i find the updation of outlet not happening.

Can i write this better? Can someone guide me to use triggers?

Answer 1

I believe your core issue is that the query

String query = "select OutletName from projectparams where projectName= '"+projectName+"' and OutletName= '"+outletName+"' group by projStatus";

Will return 1 not only if all the projects have completed but also if none have been completed (ie all the projStatus values are 1).

Additionally, as it stands if very much appears that the Outlets table is superfluous. That is all columns (bar the id, which serves no purpose) are duplicated in the projectparams table.

You can ascertain is all the tasks for a project by multiplying the number of params by 2 (the status completion value) against the sum of all of the projstatus values. If they match then all params have been set to 2.

Consider the following which is your data (but status 1 for RA_Perpsi/Tesco rows) plus some additional data where the only fully completed is for the Completed Example project (highlighted) as per :-

The using (to process all results)

-- WHERE clause removed group by projectname added (to show all results)
SELECT OutletName FROM projectparams GROUP BY projectname,projStatus;

The result is :-

• That is Ra_Pepsi/Tesco has no params completed (nothing done) but there is only one row so the project is detected as being completed. Likewise for RA_Cocola and for Some other outlet.
• Completed Example produces 1 row so is complete as it should be. Incomplete example (where it is part way through) is the only one that comes up as incomplete.

Using the above data consider the following (noting that no reference is needed to the Outlets table AND that the WHERE clause has been omitted and the GROUP BY according to projectname to show all projects) :-

SELECT 
    OutletName, 
    CASE 
        WHEN (count() * 2 - sum(projStatus)) = 0 THEN 2 ELSE 1
        END AS Status,
    (count() * 2 - sum(projStatus)) ||' of '||count() AS outstanding 
FROM projectparams 
GROUP BY projectname

This results in :-

As such there is no need for the Outlet Table the projectparams table, at least according to your example, is sufficient and as such there is no need for a trigger. Whenever an update is made you simply refresh the display using the one table and a query such as the last example.

To demonstrate your scenario step by step consider the following code (based upon the data above ie the RA_Pepsi has been added but nothing done) :-

-- First Query
SELECT 
    OutletName, 
    CASE 
        WHEN (count() * 2 - sum(projStatus)) = 0 THEN 2 ELSE 1
        END AS Status,
    (count() * 2 - sum(projStatus)) ||' of '||count() AS outstanding 
FROM projectparams 
WHERE projectname = 'RA_Pepsi'AND outletName = 'Tesco'
GROUP BY projectname
;

-- First Update
UPDATE projectparams SET projStatus = 2 WHERE param = 'shelfstrip' AND projectname = 'RA_Pepsi' AND outletName = 'Tesco';

-- 2nd Query
SELECT 
    OutletName, 
    CASE 
        WHEN (count() * 2 - sum(projStatus)) = 0 THEN 2 ELSE 1
        END AS Status,
    (count() * 2 - sum(projStatus)) ||' of '||count() AS outstanding 
FROM projectparams 
WHERE projectname = 'RA_Pepsi'AND outletName = 'Tesco'
GROUP BY projectname
;

-- 2nd Update (all completed) 
UPDATE projectparams SET projStatus = 2 WHERE param = 'shelfleft' AND projectname = 'RA_Pepsi' AND outletName = 'Tesco';


-- 3rd Query
SELECT 
    OutletName, 
    CASE 
        WHEN (count() * 2 - sum(projStatus)) = 0 THEN 2 ELSE 1
        END AS Status,
    (count() * 2 - sum(projStatus)) ||' of '||count() AS outstanding 
FROM projectparams 
WHERE projectname = 'RA_Pepsi'AND outletName = 'Tesco'
GROUP BY projectname
;

The first query shows the project with nothing done as per :-

The 2nd query (after changing the status of the shelfstrip to 2) shows :-

The 3rd query (after changing the status of the shelfleft to 2) shows :-

For Android

The foloowing code demonstrates applying the above on Android and additional uses the recommended convenience methods (they build much of the SQL, off protection against SQL injection and add additional functionality eg update returns the number of rows updated) :-

Two methods (the first using the query above, the second updating as per yours but using the update convenience method :-

public String getOutletStatus(String projectname, String outletname) {
    String rv = "Ooops nothing found!"; // default if nothing found
    String[] columns = new String[]{"outletname",
            "CASE " +
                    "WHEN (count() * 2 - sum(projStatus)) = 0 THEN 2 ELSE 1 " +
                    "END AS Status", //<<<<<<<<< the column name will be Status
            "(count() * 2 - sum(projStatus)) ||' of '||count() AS outstanding" // The column name will be outstanding
    };
    String whereclause = "projectname=? AND outletName=?";
    String[] whereargs = new String[]{projectname,outletname};
    String groupby = "projectname"; // not needed
    Cursor csr = sqliteHelper.getWritableDatabase().query("projectparams",columns,whereclause,whereargs,null,null,null);
    if (csr.moveToFirst()) {
        int statuscode = csr.getInt(csr.getColumnIndex("Status"));
        String outstanding = csr.getString(csr.getColumnIndex("outstanding"));
        String outlet = csr.getColumnName(csr.getColumnIndex("outletname"));
        String statusdescription = "incomplete";
        if (statuscode == 2) {
            statusdescription = "complete";
        }
        rv = "The status of project " + projectname + " for outlet " + outlet + " is " + statusdescription + ". With " + outstanding + ".";
    }
    csr.close();
    return rv;
}

public void updateStatus(String projectname, String outletname, String param) {
    String whereclause = "projectname=? AND outletname=? AND param=?";
    String[] whereargs = new String[]{projectname,outletname,param};
    ContentValues cv = new ContentValues();
    cv.put("projStatus",2);
    int number_of_rows_updated = sqliteHelper.getWritableDatabase().update("projectparams",cv,whereclause,whereargs);
}

They have been tested (using the base data show above) and reflect the final 3 queries with updates between them :-

    String status = getOutletStatus("RA_Pepsi","Tesco"); // Before anything
    Log.d("RESULT",status);

    updateStatus("RA_Pepsi","Tesco","shelfstrip"); //shelfstrip completed
    status = getOutletStatus("RA_Pepsi","Tesco");
    Log.d("RESULT",status);

    updateStatus("RA_Pepsi","Tesco","shelfleft"); //shelfleft completed
    status = getOutletStatus("RA_Pepsi","Tesco");
    Log.d("RESULT",status);

Result in the Log :-

04-29 12:46:09.615 20471-20471/? D/RESULT: The status of project RA_Pepsi for outlet outletname is incomplete. With 2 of 2.
04-29 12:46:09.621 20471-20471/? D/RESULT: The status of project RA_Pepsi for outlet outletname is incomplete. With 1 of 2.
04-29 12:46:09.625 20471-20471/? D/RESULT: The status of project RA_Pepsi for outlet outletname is complete. With 0 of 2.