Develop Reference

Is the sequence on how we type a Sqlite query to Create a column with attributes really matters

I'm new to coding android apps with Sqlite
I have three questions
I created this Sqlite table with columns with attributes like
TEXT
NOT NULL
UNIQUE
DEFAULT regular
Q1) I'm skeptical to know whether is there any order on how to delare attributes for a row
Q2) If I declare any row to have a default value like will the text be still inserted even though the user inserts something in that row, if yes, then how to insert a default value if the user dosen't inset any value in a specific Row
Q3)Is my code below correct ? What I desire is the row KEY_TAGNAME to be unique, not null and to have a value if the row doesn't get any data while a insert statement occurs for that table.
private static final String CREATE_TAGTABLE_SQL=
"CREATE TABLE " + DATABASE_TABLE_TAG
+ " ("
+ KEY_TAGROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ KEY_TAGNAME + " TEXT NOT NULL UNIQUE DEFAULT regular"
+ ");";

A1: I couldn't find anything in the documentation that clearly says anything about the order of the attributes but I tried to create a couple of tables in a test database I created to check this and it seems that if you do not follow the proper order you will get a syntax error.
(tried with create table test (key1 integer primary key autoincrement) which works correctly but create table test1 (key1 primary key integer autoincrement) gives a near "integer": syntax error:
A2: You can have a default value inserted that will be put if the user does not input anything there. The keyword is default and you will find more info here on how to use it (TL;DR upon table's creation you will create the row as usual and in the end put a DEFAULT and next to it the value. Please check the link on this)
A3 Your query is correct and will do the things you mention.

Column index order SQLite creates table

This is the query that I use to create a table
create table site_table(
_id integer primary key autoincrement,
name_site text,
url text,
login text,
pass text
);
I called Cursor.getColumnNames() and noticed that columns order are id, login, pass, name, url.
So, if I want a value I have to get it by the index Cursor.getString(index). Until I debugged I was messing up calling the wrong index, but now I wonder, why SQLite saves that way? Why it does not follow that way I created id, name_site, url, login and pass?
Thanks

So, if I want a value I have to get it by the index
Cursor.getString(index)
So for example for this reason you should always use
c.getString(c.getColumnIndex("ColName")); // or better getColumnIndex(CONSTANT)
This method saves all of us and ensure that you never get wrong results. Generally this method is recommended and also storing COLUMN_NAMES as CONSTANTS in separated class is very, very useful and efficient practise.
Note: Order depends on projection i.e. select name, lastname from table

That data is ordered by the order your requested it in your query, not the order you created the table with. So you probably changed the order in your query that generated said cursor.

Columns order in your cursor depends on projection. To be sure you use correct column index use c.getString(c.getColumnIndexOrThrow("COLUMN_NAME")) where c is your cursor.

I just made the experience first hand:
The indices of the columns of the cursor as a result of a
SELECT * FROM mytable WHERE ...
query have sometimes (not always) a different order that what SQLITE Database Browser shows as column order in the Database Structure tab. So referencing the columns via getColumnIndex seems to be the only safe way.

Dynamic Tables in Android SQLite

My question involves databases - The scenario is this:
I have an app that tracks when people borrow items. I have an existing table which tracks who they are, what they have borrowed and so on. What I would like to do is create a separate table to track what the person has borrowed, their contact info, if they returned it, etc.
My idea to do this would be to create a Dynamic table in SQL that would hold the records for 1 person, ie
John Smith
DVD; July 12, 2012; Returned in good condition; etc
As I'm still learning, I wanted to know if:
This is possible, feasible or if there is a smarter way of going about it.

Your answer depends on your scenario;
If you are only interested with "who" borrowed "what" (currently) and not "when" except last occurance, and you are assuming there are always only 1 copy of an item, then you can use one to one relation as:
CREATE TABLE Person
(
PersonId int IDENTITY(1,1) NOT NULL,
Name nvarchar(30) NOT NULL,
Surname nvarchar(30) NOT NULL,
BorrowItemId int NULL FOREIGN KEY REFERENCES Item UNIQUE,
BorrowDate datetime NULL,
ReturnDate datetime NULL,
ReturnCondition nvarchar(50) NULL,
CONSTRAINT PK_Person PRIMARY KEY CLUSTERED (PersonId ASC),
)
CREATE TABLE Item
(
ItemId int IDENTITY(1,1) NOT NULL,
ItemDescription nvarchar(50) NOT NULL,
CONSTRAINT [PK_Item] PRIMARY KEY CLUSTERED (ItemId ASC)
)
If you have multiple copies of each item you should remove the UNIQUE key on BorrowItemId changing relation to one to many. In case;
To see the items borrowed and returned with person information:
SELECT PersonId, Name, Surname, ItemDescription, ReturnDate, ReturnCondition
FROM Person INNER JOIN Item
ON BorrowItemId = ItemId
WHERE BorrowItemId IS NOT NULL
AND ReturnDate IS NOT NULL
You can add PersonId filter in WHERE clause to query for specific person
This isn't a good design since you can insert records without date information or you can even have records with date info but no related BorrowItemId. I suggest using many to many and keep historic data (can be handy) or overwrite using update each time the person borrows a new item

Their contact information could be linked into the table which tracks who they are.
If you have not created a table yet for the returns then I suggest you reference the borrowing table's ID and set in the borrowing table a flag to say this item has been returned.
I am not too sure why you would want to create a new table to collate all the information. If you want to get all the information together then I suggest using the SQL keywrod JOIN when preparing statements. If you really want to store the information later on in a table you can but it will just be duplicates in your database.
A tutorial on the different types of joins you can do : http://www.w3schools.com/sql/sql_join.asp

It is definitely possible to do as you describe. It really isn't a very good strategy, though. Your new table is, exactly, equivalent to an additional column in the existing table that tags the row as belonging to a specific individual.

Android: sqlite: cursor: getColumnIndex

I've got a fairly complicated query (multiple joins) on a normalized sqlite database. The query does a SELECT * to enable some automated attribute selection logic (so I can't eliminate the "*")
The problem I am having is that my result set contains multiple columns with the same attribute name. For example, one attribute common to each table in the query is "_id". When I go to call "cursor.getColumnIndex("_id")" the value returned is always the index of the last "_id" attribute in the result set column list (i.e. not the one I want). I'd love to be able to use my SQL alias prefixes like cursor.getColumnIndex("A._id") but that is not working.
QUESTIONs
It appears that cursor.getColumnIndex(AttributeName) returns the index of the last "AttributeName". Can anyone confirm this?
Also, any suggestions on how return the index of the 1st attribute with "AttributeName"? or better the Xth attribute having "AttributeName"?

You can do this:
SELECT _id as myID, * FROM myTable
This means the _id field will appear twice for each table in your results, but one of the two columns will have a unique name which should enable you to find it.

Unfortunately the documentation doesn't mention anything about what you need to do, so I am assuming it cannot be done.
However, you say
The query does a SELECT * to enable some automated attribute selection
logic (so I can't eliminate the "*")
What is this 'automated attribute selection logic' you speak of? Why do you require this?

An oder solution is:
"SELECT tableName.columnName FROM tableName"
and then do the same with:
cursor.getColumnIndex("tableName.columnName");
This is what MS-Access does. You can create a query and then see the generated SQL code (simply going to 'view' menu and selecting 'SQL view' from your query dessign window)

SQLite-how to compare two column

friends,
I am doing an Android project in my company, still some small work is remaining, I need your help to complete the task.
The problem is...
I have created two tables in which, table1 has an empty column, for purpose for saving name...
The table2 has a list of names, the objective is only the names from this list should be should be saved in the table1's empty column other than that it shouldn't accept any of the name typed manually.

You appear to want to make the list of names a validation: if the user wishes to save a name to table1, the name must already exist in table2.
Typically this would be done as in the following example, in which only the products listed in PRIZEPRODUCTS can be entered into PRIZEWINNERS table: someone could not win a Boat, for example, given the data below:
PRIZEPRODUCTS
id
productname
1|TV
2|iPad
3|backpack
PRIZEWINNERS
id
productid
winner
ALTER TABLE PRIZEWINNERS
ADD CONSTRAINT PRIZEWINNERS_PRIZEPRODUCTS_FK
FOREIGN KEY(productid) REFERENCES PRIZEPRODUCTS(id)
SQLite doesn't create the foreign key using ALTER TABLE but as part of the create-table statement. See here for the syntax. For enabling foreign key support in Android (2.2), see here.
Now, you can establish the foreign key on the [productname] column if [productname] were the key of PRIZEPRODUCTS. In other words, you could make person-name the key of the table rather than having a PersonID. But if that name is changed in the validation table, it can break the foreign key relationship, unless ON UPDATE CASCADE is enabled, but I am not sure if this is supported in Android.

I hope below query will work for you.
insert into table1(name) values (select name from table2 where id=?).
Thanks.