As you know well if i delete entries from a db or completely clear that db, id is autoincremented from where it is left. How can I prevent this- I mean I want my database dont erase the last id's for example even id=2 is removed next id should be id=3. thanks
Declare your id field INTEGER PRIMARY KEY AUTOINCREMENT. That should prevent re-use of id values. (See https://sqlite.org/autoinc.html)
Related
Below I have a users table and I want it so that every time a row's avatar changes to a different value, the same row's downloadavatar is set to 1.
CREATE TABLE users (
id UNIQUE TEXT,
avatar TEXT,
downloadavatar INTEGER
)
CREATE TRIGGER update_users_downloadavatar AFTER UPDATE OF avatar ON users WHEN old.avatar!=new.avatar
BEGIN
UPDATE users SET downloadavatar=1 WHERE id=old.id;
END
The SQL above does just that. My question is will it result in searching the entire users table for the row that meets the WHERE condition despite the TRIGGER already knowing where it is? If yes, how can I rectify this inefficiency?
The trigger does not know where the row is; it just knows how it is identified.
Looking up the row by ID will use the index, and because of the previous lookup done by the UPDATE, the few pages needed are already in the cache.
To avoid going through the index, use the rowid instead of the id column.
So I have a table with data about an image. The table looks something like this...
ROWID|title|description|file_path
The file path contains the name of the image. I want to rename the image to match the ROWID.
How do I get the latest ROWID? I need to also account for rows that have been deleted as I am using this as an autoincremented primary key. Because, if a row within the table has been deleted it is possible for the table to look like this...
1|title A|description A|..\fileA.jpg
2|title B|description B|..\fileB.jpg
5|title E|description E|..\fileE.jpg
7|title G|description G|..\fileG.jpg
On top of that there could be one or more rows that have been deleted so the next ROWID could be 10 for all I know.
I also need to account for an fresh new table or a table that has had all data deleted and the next ROWID could be 1000.
In summary, I guess the real question is; Is there a way to find out what the next ROWID will be?
If you have specified AUTOINCREMENT in primary key field and table is not empty this query will return latest ROWID for table MY_TABLE:
SELECT seq
FROM sqlite_sequence
WHERE name = 'MY_TABLE'
What language? Looks like the c API has the following function:
sqlite3_int64 sqlite3_last_insert_rowid(sqlite3*);
http://www.sqlite.org/c3ref/last_insert_rowid.html
You could also just do:
select MAX(rowid) from [tablename];
Unfortunately neither of these methods completely worked the way I needed them to, but what i did end up doing was....
insert data into table with the fields I needed the rowid for filled with 'aaa'
then updated the rows with the data.
This seemed to solve my current issue. Hopefully it doesn't cause another issue down the road.
I think last_insert_rowid is what you want, usually.
Note that the rowid behavior is different depending on the autoincrement flag - either it will monotonically increase, or it will assume any free id. This will not usually affect any smaller use cases though.
I have two different CSV files which I have merged and imported into a single table in a SQLite3 database. Each CSV file contained a column called ID. Since, some of the ID's are duplicates (across the CSV files) and this is a primary key field, I need a way to completely renumber the ID field for each row in the table.
The ID field is also an auto-increment field.
So, what I would like to do is to run a SQL command or some other method where the ID for each row of the table would be reset to ensure uniqueness. For example, the ID field for the first row will be set to 1 the next to 2 and so on.
Note, it is not so important that it begin with 1. Ensuring primary key uniqueness is the goal here. It doesn't matter what number it starts at. There are also no foreign key relations so that is not an issue.
Any suggestions much appreciated.
Okay, in my case, I figured out that it was easiest to not import the ID column. Rather, I imported everything else and then added an ID field of type auto-increment. Once I did that, everything was re-numbered as I wanted.
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 have an iPhone app and one of my users found a really strange problem with my application. I can't reproduce the problem and I can't figure out why it's happening. Maybe you can?
In Sqlite I have a table with about 1000 rows, each with a unique id. But for some reason the id of that table has restarted, before it was around 1000 but now it's restarted from 80 something. So everytime the user inserts a new row the new assigned id starts around 80 something and I get two duplicates ids that should be unique and yeah you can understand the problem. I have looked at all queries that does anything to that table and none of them could have done this. I always relay on the built in mechanism where the ids are assigned automatically.
Have you seen anything like this?
The schema of the table looks like this:
CREATE TABLE mytable(
id INTEGER PRIMARY KEY
);
As you can see I don't use AUTOINCREMENT. But from what I understand even if the user deletes a row with id 80, it is ok to give a new inserted row id 80 but not like it works now where the database just keeps incrementing the ids even if I have already have rows with the same id. Shouldn't it work like this:
HIGHEST ROWID IS 1000, ALL IDS FROM 0-1000 ARE TAKEN
USER DELETES ROW WITH ID 80
INSERT A NEW ROW
THE ID OF THE INSERTED ROW MIGHT NOW BE 80
SETS THE ID OF THE INSERTED ROW TO 80
INSERT A NEW ROW
THE ID OF THE INSERTED ROW CAN NOT BE 81 AS THIS IS ALREADY TAKEN
SETS THE ID OF THE INSERTED ROW TO 1001
Isn't that how it should work?
Did you declare your id column as a(n autoincrementing) primary key?
CREATE TABLE mytable(
id INTEGER PRIMARY KEY AUTOINCREMENT
);
By adding the autoincrement keyword you ensure that all keys generated will be unique over the lifetime of your table. By omitting it, the keys will still be unique, but it may generate keys that have already been used by other, deleted entries. Note that using autoincrement can cause problems, so read up on it before you add it.
Edit This is a bit of a long-shot, but sqlite only supports one primary key per table. If you have more than one primary key declared, you need to declare all but the one you actually want to use as a primary key as "unique". Hence
CREATE TABLE mytable(
id INTEGER PRIMARY KEY,
otherId INTEGER UNIQUE
);
Hard to say without the code and schema, but my instinct is that this unique ID is not defined as either unique nor primary key, which they should.
How do you make sure (in theory) id's are unique? What is your insert query like?