android _Displaying a record from a sqlite database - android

I am planning to build an app that lets the user select a record from a particular database such as:
name favorite_color favorite_team
sue red Dal
mike blue Mia
sam purple Bal
My problem is that most of the tutorials that I have come across only demonstrates examples using a table with one column. What if my pre-populated database more then on column? What if it had 100 columns? Does anyone know how this is done?????


Here's an example:
Step1:Declare SQLiteDatabase,Declare Databasehelper
Step2:Declare string or number which is to be used as key or get it as an intent(in this example 'rowid'
Step 3: In the OnCreate method add lines of code similar to following:
String query="select * from my_table_name where _id="+rowid;
Cursor myCursor = database.rawQuery(query,null);
myCursor.moveToFirst();
//This line implies i am getting data from column four of selected row
String x=myCursor.getString(4);
//This line implies i am getting data from column two of selected row
String y=myCursor.getString(4);
myCursor.close();
Note:
a)Don't forget that your database size must not exceed 1.2mb
b)Also include a column with name _id which auto-increments in each table that you are using,you may use sqlite browser to do so
c)also create the following table in your database :
CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT 'en_US')
Now insert a single row with the text 'en_US' in the "android_metadata" table
INSERT INTO "android_metadata" VALUES ('en_US')


read this you will learn every thing you need to know. One other way to access db information is using an ORM like ormlite. I'm using it in various apps that i've developed, and it's simple to use.

Related

SQLite Check if Table is FTS4

I'm developing an Android app that uses a SQLite database with FTS4 tables.
In the app there's an option to import a database from the external memory. This database needs to be checked to confirm that it has all the correct tables and columns. I already have the code to do that however I don't know how to check if the tables are "normal" or FTS4. This will result in problems later on with queries with MATCH on them.
The only way I can think of to check if the tables are FTS4 is to do a random query with MATCH and if it gets an error it's because they are not.
Is there a better way to do this like with just a command?

Using MATCH on a plain table results in an error message only if the table has at least one row.
FTS table have a virtual column with the same name as the table name. So you could try a query like SELECT MyTable FROM MyTable.
You could check whether the shadow tables (MyTable_content, MyTable_segdir, etc.) exist.
You could check the CREATE TABLE statement in the system table: SELECT sql FROM sqlite_master WHERE type = 'table' AND name = 'MyTable';

Android Sqlite Database Formation

In my application I take entry from user as :-
Name:- -------------------------
Favorite Fruit:- a)
b)
c)
--------- Add More ----------
Then I want to save it into a Sqlite database. Now I provide user to type in edittext search like this:-
Search Fruit:- Apple,Banana
And then I want to query my database and Print the name of those who like atleast Apple and Banana.
Now my issue is how do I make my database columns to achieve results faster.
Should I make two columns Name and FruitsLiked or something else. Because if I make only two colums then how do I search into database.
Thanks

Create one table n two columns. First column is for name , second one comma separated list of fruits.
Then as db query use like keyword based query

How to create dynamic database table in SQLite

I am trying to create one application to store information in sq-lite table.
But i want to take table information from user like table name, columns name, and number of columns, also user can edit that by table name, delete column add new column.
how can i do it.
i add example screen for table filed

Android allows you to execute arbitrary SQL strings. Construct a SQL strings from your UI and then input the string into a command similar to db.execute(string).
Reference

Android SQLite Database: adding columns after DB is created

I'm a bit unfamiliar with updating SQLite Databases after I have created them. Is it relatively easy to add new columns and update values in the rows? Like adding an email or twitter name column to a contact list app. Or could I set up columns with the name "Col1, Col2, etc" to have extra for later and then when I want to use those columns add them into my queries/cursors in my app such that KEY_EMAIL is "Col15" or whatever.

Sqlite supports a limited subset of the ALTER TABLE command. You can rename a table or add a new column. So you can't rename or delete a column or remove constraints after you've created the table (at least not with sql-commands).
So, no need to add "spare"-columns. In fact, since you can't remove columns, that'd be a bad idea.
SQL As Understood By SQLite

Can you delete columns in an SQLite database?

The Android app that I am currently working on dynamically adds columns to an SQLite database. The problem I have is that I cannot figure out a way to remove these columns from the database.
If I add column A, B, C, D, and E to the database, is it possible to later remove column C?
I have done a lot of looking around and the closest thing I could find was a solution that requires building a backup table and moving all the columns (except the one to be deleted) into that backup table.
I can't figure out how I would do this, though. I add all the columns dynamically so their names are not defined as variables in my Java code. There doesn't seem to be a way to retrieve a column name by using Android's SQLiteDatabase.

SQLite has limited ALTER TABLE support that you can use to add a column to the end of a table or to change the name of a table.
If you want to make more complex changes in the structure of a table, you will have to recreate the table. You can save existing data to a temporary table, drop the old table, create the new table, then copy the data back in from the temporary table.
For example, suppose you have a table named "t1" with columns names "a", "b", and "c" and that you want to delete column "c" from this table. The following steps illustrate how this could be done:
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;

SQLite doesn't support a way to drop a column in its SQL syntax, so its unlikely to show up in a wrapper API. SQLite doesn't often support all features that traditional databases support.
The solutions you've identified make sense and are ways to do it. Ugly, but valid ways to do it.
You can also 'deprecate' the columns and not use them by convention in newer versions of your app. That way older versions of your app that depend on column C won't break.

Oh... just noticed this comment:
The app is (basically) an attendance tracking spreadsheet. You can add
a new "event" and then indicate the people that attended or didn't.
The columns are the "events".
Based on that comment you should just create another table for your events and link to it from your other table(s). You should never have to add columns to support new domain objects like that. Each logical domain object should be represented by its own table. E.g. user, location, event...
Was writing this initially. Will keep it if you're interested:
Instead of dynamically adding and removing columns you should consider using an EAV data model for that part of your database that needs to be dynamic.
EAV data models store values as name/value pairs and the db structure never needs to change.

Based on your comment below about adding a column for each event, I'd strongly suggest creating a second table in which each row will represent an event, and then tracking attendance by storing the user row id and the id of the event row in the attendance table. Continually piling columns onto the attendance table is a definite anti-pattern.

With regards to how to find out about the table schema, you can query the sqlite_master table as described in this other SO question - Is there an SQLite equivalent to MySQL's DESCRIBE [table]?

As per SQLite FAQ, there is only limited support to the ALTER TABLE SQL command. So, the only way you can do is that ou can save existing data to a temporary table, drop the old table, create the new table, then copy the data back in from the temporary table.
Also you can get the column name from the database using a query. Any query say "SELECT * FROM " gives you a cursor object. You can use the method
String getColumnName(int columnIndex);
or
String[] getColumnNames();
to retrieve the names of the columns.

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