I have a object that contains data from a DB. The object has a ID, which in the DB is auto increment field. When creating an object i dont know his ID, until i insert a new record to the DB. Then i want to get back the auto generated value of ID field.
I tried to do so by adding a Output parameter, but SQLite.NET throws a NotSupportedException when i try to set the Direction to ParameterDirection.Output.
What can i do? The other fields except ID are not unique.
A other option is to auto increment manually, in the program, but it seems to be a bit complicated to implement.
Thanks a lot.
SELECT last_insert_rowid();
This will get the last inserted ROWID. If the table has a column of type INTEGER PRIMARY KEY then that column is another alias for the rowid.
Related
I've seen enough answers to know you can't easily check for columns in SQLITE before adding. I'm trying to make a lazy person's node in Node-Red where you pass a message to SQLITE which is the query. Adding a table if it does not exist is easy.
msg.topic='create table IF NOT EXISTS fred (id PRIMARY KEY);'; node.send(msg);
it occurred to me that adding a table which had the names of the fields would be easy - and if the field name is not in the table.... then add the field. BUT you can't add multiple fields at once - so I can't do this...
msg.topic='create table IF NOT EXISTS fred (id PRIMARY KEY, myfields TEXT);'; node.send(msg);
The problem with THAT is that I can't add this in later, there's no way to check before adding a field it the table exists!
This is what I WANT
msg.topic='create table IF NOT EXISTS fred (id PRIMARY KEY, myfields TEXT);'; node.send(msg);
msg.topic='if not (select address from myfields) alter table fred add column address text';
I just cannot think of any way to do this - any ideas anyone (the idea is that the node-red node would input a table, field and value and if the table didn't exist it would be created, if the field didn't exist it would be created, all before trying to add in the value).
You won't be able to make the ALTER TABLE conditional in the SQL itself. You'll need to handle that from your calling script.
Alternately, simply attempt to add the column to the table and accept failure as an outcome. Assuming the table exists, the only failure reason you could encounter is that the column already exists.
If you'd like to do something more graceful, you can check if the column exists in advance, then conditionally run the SQL from your calling application.
I'm not sure that I'm getting an id primary key in my sqlite table.
When I create my table I use
CREATE TABLE IF NOT EXISTS HABITS (id unique, uid, text, orglvl, habitstatus)
The other properties are fine, and I can retrieve results.rows.item(i).text, but results.rows.item(i).id is NULL
Also upon Insert, when I try to get results.insertId, I get an error of "undefined", which started this whole wondering for me.
What am I doing wrong - how come I have no id's when I have created them in my table?
To get an autoincrementing column, you must use INTEGER PRIMARY KEY.
I use a database in my project and when i insert values into a table i need to check if the field already has a value that does not produce an insert.
for exemple:
INSERT INTO myTable (column1) values ('some_value1')
if some_value1 alredy exists in column1 do not insert the value.
Put a unique constraint on myTable.column1. Then, whenever you try to insert a duplicate value, it won't let you as it violates the constraint. You can either catch and handle this error, or just let the DB engine do it's thing automatically.
EDIT: Note that SQLite doesn't allow you to do many alterations to your table, once it's created; so you may have to recreate your table with the constraint in place.
I believe this can be handled using the conflict resolution IGNORE method on SQLite. The code below should do the trick. The column1 here should be set to unique for this.
INSERT OR IGNORE INTO myTable (column1) values ('some_value1')
I'm using the following links for reference;
http://www.sqlite.org/lang_insert.html
http://www.sqlite.org/lang_conflict.html
I have a SQLite table that looks like this:
CREATE TABLE Cards (id INTEGER PRIMARY KEY, name TEXT)
So each time I create a new row, SQLite is going to automatically assign it a unique ID.
However, if I delete a row and then create a new row, the new row is going to have the ID of the previously deleted row.
How can I make sure it doesn't happen? Is it possible to somehow force SQLite to always give really unique IDs, that are even different from previously deleted rows?
I can do it in code but I'd rather let SQLite do it if it's possible. Any idea?
Look at autoincrement (INTEGER PRIMARY KEY AUTOINCREMENT). It will guarantee this and if the request can't be honored it will fail with SQLITE_FULL.
I want to insert a record into a sqlite table if its actually not inserted.
Let's say it has three fields pk, name, address
I want to INSERT new record with name if that name not added preveously.
Can we do with this in a single Query. Seems like its slightly different from SQL Queries sometimes.
Yes, you can do that with a single query.
INSERT ON CONFLICT IGNORE should help you: http://www.sqlite.org/lang_conflict.html
Put a unique key on the name, this will create a conflict when you try inserting a record if the name already exists.
The default is ABORT, so without the IGNORE, the statement will return an error. If you don't want that, use IGNORE.
If you can't make use of a UNIQUE INDEX in combination with INSERT INTO or INSERT OR IGNORE INTO, you could write a query like this;
INSERT INTO table (column)
SELECT value
WHERE NOT EXISTS (SELECT 1
FROM table
WHERE column = value)