Develop Reference

SQLite set field to same value as generated id at insert

We have a requirement where some fields in a table need to have the same value as their ID. Unfortunately, we currently have to insert a new record and then, if needed, run another update to set the duplicate field (ID_2) value to equal the ID.
Here is the Android Sqlite code:
mDb.beginTransaction();
// ... setting various fields here ...
ContentValues contentValues = new ContentValues();
contentValues.put(NAME, obj.getName());
// now insert the record
long objId = mDb.insert(TABLE_NAME, null, contentValues);
obj.setId(objId);
// id2 needs to be the same as id:
obj.setId2(objId);
// but we need to persist it so we update it in a SECOND call
StringBuilder query = new StringBuilder();
query.append("update " + TABLE_NAME);
query.append(" set " + ID_2 + "=" + objId);
query.append(" where " + ID + "=" + objId);
mDb.execSQL(query.toString());
mDb.setTransactionSuccessful();
As you can see, we are making a second call to set ID_2 to the same value of ID. Is there any way to set it at INSERT time and avoid the second call to the DB?
Update:
The ID is defined as follows:
ID + " INTEGER PRIMARY KEY NOT NULL ," +

The algorithm used for autoincrementing columns is documented, so you could implement it manually in your code, and then use the new value for the INSERT.

This is quite a ugly hack, but it may be possible :
with id_table as (
select coalesce(max(seq), 0) + 1 as id_column
from sqlite_sequence
where name = 'MY_TABLE'
)
insert into MY_TABLE(ID_1, ID_2, SOME, OTHER, COLUMNS)
select id_column, id_column, 'SOME', 'OTHER', 'VALUES'
from id_table
It only works if the table ID is an AUTOINCREMENT, and is therefore managed via the documented sqlite_sequence table.
I also have no idea what happen in case of concurrent executions.

You could use an AFTER INSERT TRIGGER e.g.
Create your table (at least for this example) so that ID_2 is defined as INTEGER DEFAULT -1 (0 or any negative value would be ok)
e.g. CREATE TABLE IF NOT EXISTS triggertest (_id INTEGER PRIMARY KEY ,name TEXT ,id_2 INTEGER DEFAULT -1);
Then you could use something like (perhaps when straight after the table is created, perhaps create it just before it's to be used and drop it after done with it ) :-
CREATE TRIGGER triggertesting001
AFTER INSERT ON triggertest
BEGIN
UPDATE triggertest SET id_2 = `_id`
WHERE id_2 = -1;
END;
Drop using DROP TRIGGER IF EXISTS triggertesting001;
Example usage (testing):-
INSERT INTO triggertest (name) VALUES('Fred');
INSERT INTO triggertest (name) VALUES('Bert');
INSERT INTO triggertest (name) VALUES('Harry');
Result 1 :-
Result 2 (trigger dropped inserts run again ):-
Result 3 (created trigger) same as above.
Result 4 (ran inserts for 3rd time) catch up i.e. 6 rows updated id_2 with _id.
I'd strongly suggest reading SQL As Understood By SQLite - CREATE TRIGGER
Alternative solution
An alternative approach could be to simply use :-
Before starting transaction, retrieve mynextid from table described below
ContentValues contentValues = new ContentValues();
contentValues.put(ID,mynextid);
contentvalues.put(ID_2,mynextid++);
contentValues.put(NAME, obj.getName());
Then at end of the transactions update/store the value of mynextid in a simple single column, single row table.
i.e. you are managing the id's (not too dissimilar to how SQLite manages id's when 'AUTOINCREMENT' is specified)

New Column added to a table doesnt show up in query

I am adding a new column to an existing table and adding a new entry to the table with valid data present only in new column (other column being 0 by default)
Adding Column :
final String DB_ADD_COLUMN_STATEMENT_TABLE_SHOP_NAME =
"ALTER TABLE "+ shopName + " ADD COLUMN "+ "D" + time + " FLOAT";
try {
mDB.beginTransaction();
//SQLiteStatement statement = mDB.compileStatement(DB_ADD_COLUMN_STATEMENT_TABLE_SHOP_NAME);
//statement.execute();
mDB.execSQL(DB_ADD_COLUMN_STATEMENT_TABLE_SHOP_NAME);
mDB.setTransactionSuccessful();
}
catch (Exception e) {
Log.d(LOG_TAG,"addItemSample : Exception while adding column to table!!");
}
finally {
mDB.endTransaction();
}
Adding a new entry to the table with data only in this column succeeds.
But when I query the table , this new column doesn't show up in the cursor.
Though the adding column and querying happen in different threads, they are serialized from the way they are being called from my code (ie first column is added and then db is queried) and also the I am using a single connection to db.
I wondering what might be reason for this?
PS:When db query is performed immediately after inserting the column , it shows up.

depends on your query statement.
is it like
String query="select id, column1, column 2 from "+shopName+" where yourcondition";
?
may be you have to add column?
String query="select id, column1, column2, D192200 from "+shopName+"";
or you may query all columns
String query="select * from "+shopName+"";

The issue could be that you are adding a column that expects NOT NULL values
Try something like this:
ALTER TABLE "+ shopName + " ADD COLUMN "+ "D" + time + " FLOAT" default 0 NOT NULL;
Use which ever default value you need and update the values as needed.

How to bind values to SQLiteStatement for insert query?

Insertion code using SQLiteStatement usually looks like this,
String sql = "INSERT INTO table_name (column_1, column_2, column_3) VALUES (?, ?, ?)";
SQLiteStatement statement = db.compileStatement(sql);
int intValue = 57;
String stringValue1 = "hello";
String stringValue2 = "world";
// corresponding to each question mark in the query
statement.bindLong(1, intValue);
statement.bindString(2, stringValue1);
statement.bindString(3, stringValue2);
long rowId = statement.executeInsert();
Now this works perfectly fine but the issue I find here is that I have to be very careful about binding correct data to corresponding indexes. A simple swap of index will give me an error.
Also let's say in future my column_2 gets dropped from the table, then I would have to change all the indexes after the column_2 index otherwise the statement won't work. This seems trivial if I just have 3 columns. Imagine if a table has 10-12 (or even more) columns and column 2 gets dropped. I'll have to update the index of all the subsequent columns. This whole process seems inefficient and error prone.
Is there an elegant way to handle all this?
Edit : Why would I want to use SQLiteStatement ? Check this :Improve INSERT-per-second performance of SQLite?

Insertions can be done with ContentValues:
ContentValues cv = new ContentValues();
cv.put("column_1", 57);
cv.put("column_2", "hello");
cv.put("column_3", "world");
long rowId = db.insertOrThrow("table_name", null, cv);
But in the general case, the most correct way would be to use named parameters. However, these are not supported by the Android database API.
If you really want to use SQLiteStatement, write your own helper function that constructs it from a list of columns and takes care of matching it with the actual data. You also could write your own bindXxx() wrapper that maps previously-saved column names to parameter indexes.

You can use ContentValues with beginTransaction into SQLite that is quite easy as well as faster then prepared statements
For this you have to create ContentValues Array previously or create Content values object into your loop. and pass into insert method .this solution solve your both of problem in one.
mDatabase.beginTransaction();
try {
for (ContentValues cv : values) {
long rowID = mDatabase.insert(table, " ", cv);
if (rowID <= 0) {
throw new SQLException("Failed to insert row into ");
}
}
mDatabase.setTransactionSuccessful();
count = values.length;
} finally {
mDatabase.endTransaction();
}

SQlite AUTOINCREMENT with Statement Binding

Created a table
"CREATE TABLE student ( id INTEGER PRIMARY KEY AUTOINCREMENT, name
TEXT, course TEXT)"
Now when trying to insert a row like
String sql = "INSERT INTO student" +" VALUES (?,?)";
SQLiteStatement statement = myWriteableDatabase.compileStatement(sql);
statement.clearBindings();
statement.bindString(2, "Some Name");
statement.bindString(3, "Some Course");
statement.execute();
this throws an exception saying
table student has 3 columns but 2 values were supplied: , while compiling: INSERT INTO student VALUES (?,?);
Why is this exception even though I have made id column as AUTOINCREMENT.

The PRIMARY KEY autogeneration only kicks in if a NULL is inserted into the column.
Either specify the columns you want to insert to:
INSERT INTO student(name,course) VALUES ...
so that the id column gets a NULL default value, or explicitly insert a NULL value, for example
INSERT INTO student VALUES(NULL,?,?)
Also check your bind indices. They are not correct - it's the index of the ? in the query string, not the index of the column in the table.

First you have an error in yours bindString calls, you only have 2 ? signs in your query, the first make reference to the name column and the second ? make reference to the course column.
If you want use the query like this:
INSERT INTO student VALUES ('name', 'course')
you need change your code to (see the query):
String sql = "INSERT INTO student" +" VALUES (NULL, ?,?)";
SQLiteStatement statement = myWriteableDatabase.compileStatement(sql);
statement.clearBindings();
statement.bindString(1, "Some Name");
statement.bindString(2, "Some Course");
statement.execute();
Or you can use this query:
INSERT INTO student (name, course) VALUES ('first', 'second')
In this case you can use this code:
String sql = "INSERT INTO student (name, course)" +" VALUES (?,?)";
SQLiteStatement statement = myWriteableDatabase.compileStatement(sql);
statement.clearBindings();
statement.bindString(1, "Some Name");
statement.bindString(2, "Some Course");
statement.execute();

Insert null in Sqlite table

I am trying to figure how to insert a null value into an SQLite table in Android.
This is the table:
"create table my table (_id integer primary key autoincrement, " +
"deviceAddress text not null unique, " +
"lookUpKey text , " +
"deviceName text , " +
"contactName text , " +
"playerName text , " +
"playerPhoto blob " +
");";
I wanted to use a simple Insert command via execSQL but since one of the values is a blob I can't do it (I think).
So, I am using a standard db.Insert command.
How do I make one of the values null?
If I just skip it in the ContentValues object will it automatically put a null value in the column?

You can use ContentValues.putNull(String key) method.

Yes, you can skip the field in ContentValues and db.insert will set it NULL.
Also you can use the other way:
ContentValues cv = new ContentValues();
cv.putNull("column1");
db.insert("table1", null, cv);
this directrly sets "column1" NULL. Also you can use this way in update statement.

I think you can skip it but you can also put null, just make sure that when you first create the Database, you don't declare the column as "NOT NULL".

In your insert query string command, you can insert null for the value you want to be null. This is C# as I don't know how you set up database connections for Android, but the query would be the same, so I've given it for illustrative purposes I'm sure you could equate to your own:
SQLiteConnection conn = new SQLiteConnection(SQLiteConnString());
// where SQLiteConnString() is a function that returns this string with the path of the SQLite DB file:
// String.Format("Data Source={0};Version=3;New=False;Compress=True;", filePath);
try
{
using (SQLiteCommand cmd = conn.CreateCommand()
{
cmd.CommandText = "INSERT INTO MyTable (SomeColumn) VALUES (null)";
cmd.ExecuteNonQuery();
}
}
catch (Exception ex)
{
// do something with ex.ToString() or ex.Message
}