SQLite UPSERT UPDATE OR INSERT

Question

I need to perform UPSERT   INSERT OR UPDATE against a SQLite Database   There is the command INSERT OR REPLACE which in many cases can be useful  But if you want to keep your id s with autoincrement in place because of foreign keys  it does not work since it deletes the row  creates a new one and consequently this new row has a new ID   This would be the table   players -  primary key on id  user name unique      id     user name    age     ------------------------------    1982     johnny     23         1983     steven     29         1984     pepee      40

User · Answer

You can also just add an ON CONFLICT REPLACE clause to your user_name unique constraint and then just INSERT away, leaving it to SQLite to figure out what to do in case of a conflict. See:https://sqlite.org/lang_conflict.html.

Also note the sentence regarding delete triggers: When the REPLACE conflict resolution strategy deletes rows in order to satisfy a constraint, delete triggers fire if and only if recursive triggers are enabled.

User · Answer

Q amp A Style Well  after researching and fighting with the problem for hours  I found out that there are two ways to accomplish this  depending on the structure of your table and if you have foreign keys restrictions activated to maintain integrity  I d like to share this in a clean format to save some time to the people that may be in my situation   Option 1  You can afford deleting the row In other words  you don t have foreign key  or if you have them  your SQLite engine is configured so that there no are integrity exceptions  The way to go is INSERT OR REPLACE  If you are trying to insert update a player whose ID already exists  the SQLite engine will delete that row and insert the data you are providing  Now the question comes  what to do to keep the old ID associated  Let s say we want to UPSERT with the data user name  steven  and age 32  Look at this code  INSERT INTO players  id  name  age   VALUES       coalesce  select id from players where user name  steven                  select max id  from drawings    1       32   The trick is in coalesce  It returns the id of the user  steven  if any  and otherwise  it returns a new fresh id   Option 2  You cannot afford deleting the row After monkeying around with the previous solution  I realized that in my case that could end up destroying data  since this ID works as a foreign key for other table  Besides  I created the table with the clause ON DELETE CASCADE  which would mean that it d delete data silently  Dangerous  So  I first thought of a IF clause  but SQLite only has CASE  And this CASE can t be used  or at least I did not manage it  to perform one UPDATE query if EXISTS select id from players where user name  steven    and INSERT if it didn t  No go  And then  finally I used the brute force  with success  The logic is  for each UPSERT that you want to perform  first execute a INSERT OR IGNORE to make sure there is a row with our user  and then execute an UPDATE query with exactly the same data you tried to insert  Same data as before  user name  steven  and age 32  -- make sure it exists INSERT OR IGNORE INTO players  user name  age  VALUES   steven   32     -- make sure it has the right data UPDATE players SET user name  steven   age 32 WHERE user name  steven     And that s all  EDIT As Andy has commented  trying to insert first and then update may lead to firing triggers more often than expected  This is not in my opinion a data safety issue  but it is true that firing unnecessary events makes little sense  Therefore  a improved solution would be  -- Try to update any existing row UPDATE players SET age 32 WHERE user name  steven    -- Make sure it exists INSERT OR IGNORE INTO players  user name  age  VALUES   steven   32

User · Answer

The problem with all presented answers it complete lack of taking triggers  and probably other side effects  into account  Solution like  INSERT OR IGNORE     UPDATE       leads to both triggers executed  for insert and then for update  when row does not exist   Proper solution is  UPDATE OR IGNORE     INSERT OR IGNORE       in that case only one statement is executed  when row exists or not

User · Answer

Option 1  Insert -  Update  If you like to avoid both changes   0 and INSERT OR IGNORE even if you cannot afford deleting the row - You can use this logic   First  insert  if not exists  and then update by filtering with the unique key   Example  -- Table structure CREATE TABLE players       id        INTEGER       PRIMARY KEY AUTOINCREMENT      user name VARCHAR  255  NOT NULL                             UNIQUE      age       INTEGER       NOT NULL     -- Insert if NOT exists INSERT INTO players  user name  age  SELECT  johnny   20 WHERE NOT EXISTS  SELECT 1 FROM players WHERE user name  johnny  AND age 20    -- Update  will affect row  only if found  -- no point to update user name to  johnny  since it s unique  and we filter by it as well UPDATE players  SET age 20  WHERE user name  johnny     Regarding Triggers  Notice  I haven t tested it to see the which triggers are being called  but I assume the following   if row does not exists   BEFORE INSERT INSERT using INSTEAD OF AFTER INSERT BEFORE UPDATE UPDATE using INSTEAD OF AFTER UPDATE   if row does exists   BEFORE UPDATE UPDATE using INSTEAD OF AFTER UPDATE   Option 2  Insert or replace - keep your own ID  in this way you can have a single SQL command  -- Table structure CREATE TABLE players       id        INTEGER       PRIMARY KEY AUTOINCREMENT      user name VARCHAR  255  NOT NULL                             UNIQUE      age       INTEGER       NOT NULL     -- Single command to insert or update INSERT OR REPLACE INTO players   id  user name  age   VALUES   SELECT id from players WHERE user name  johnny  AND age 20            johnny           20     Edit  added option 2

User · Answer

This is a late answer  Starting from SQLIte 3 24 0  released on June 4  2018  there is finally a support for UPSERT clause following PostgreSQL syntax   INSERT INTO players  user name  age    VALUES  steven   32     ON CONFLICT user name     DO UPDATE SET age excluded age       Note  For those having to use a version of SQLite earlier than 3 24 0  please reference this answer below  posted by me   MarqueIV        However if you do have the option to upgrade  you are strongly encouraged to do so as unlike my solution  the one posted here achieves the desired behavior in a single statement  Plus you get all the other features  improvements and bug fixes that usually come with a more recent release

User · Answer

Here s an approach that doesn t require the brute-force  ignore  which would only work if there was a key violation   This way works based on any conditions you specify in the update   Try this     -- Try to update any existing row UPDATE players SET age 32 WHERE user name  steven    -- If no update happened  i e  the row didn t exist  then insert one INSERT INTO players  user name  age  SELECT  steven   32 WHERE  Select Changes     0     How It Works  The  magic sauce  here is using Changes   in the Where clause   Changes   represents the number of rows affected by the last operation  which in this case is the update   In the above example  if there are no changes from the update  i e  the record doesn t exist  then Changes     0 so the Where clause in the Insert statement evaluates to true and a new row is inserted with the specified data   If the Update did update an existing row  then Changes     1  or more accurately  not zero if more than one row was updated   so the  Where  clause in the Insert now evaluates to false and thus no insert will take place   The beauty of this is there s no brute-force needed  nor unnecessarily deleting  then re-inserting data which may result in messing up downstream keys in foreign-key relationships   Additionally  since it s just a standard Where clause  it can be based on anything you define  not just key violations  Likewise  you can use Changes   in combination with anything else you want need anywhere expressions are allowed

User · Answer

To have a pure UPSERT with no holes  for programmers  that don t relay on unique and other keys   UPDATE players SET user name  gil   age 32 WHERE user name  george    SELECT changes      SELECT changes   will return the number of updates done in the last inquire  Then check if return value from changes   is 0  if so execute   INSERT INTO players  user name  age  VALUES   gil   32

[database] SQLite UPSERT / UPDATE OR INSERT

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