INSERT IF NOT EXISTS ELSE UPDATE?

Have a look at http://sqlite.org/lang_conflict.html.

You want something like:

insert or replace into Book (ID, Name, TypeID, Level, Seen) values
((select ID from Book where Name = "SearchName"), "SearchName", ...);

Note that any field not in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: In the replacement case the statement would set it to NULL and then a fresh ID would be allocated.

This approach can also be used if you want to leave particular field values alone if the row in the replacement case but set the field to NULL in the insert case.

For example, assuming you want to leave Seen alone:

insert or replace into Book (ID, Name, TypeID, Level, Seen) values (
   (select ID from Book where Name = "SearchName"),
   "SearchName",
    5,
    6,
    (select Seen from Book where Name = "SearchName"));

You should use the INSERT OR IGNORE command followed by an UPDATE command: In the following example name is a primary key:

INSERT OR IGNORE INTO my_table (name, age) VALUES ('Karen', 34)
UPDATE my_table SET age = 34 WHERE name='Karen'

The first command will insert the record. If the record exists, it will ignore the error caused by the conflict with an existing primary key.

The second command will update the record (which now definitely exists)

You need to set a constraint on the table to trigger a "conflict" which you then resolve by doing a replace:

CREATE TABLE data   (id INTEGER PRIMARY KEY, event_id INTEGER, track_id INTEGER, value REAL);
CREATE UNIQUE INDEX data_idx ON data(event_id, track_id);

Then you can issue:

INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 2, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 5);

The "SELECT * FROM data" will give you:

2|2|2|3.0
3|1|2|5.0

Note that the data.id is "3" and not "1" because REPLACE does a DELETE and INSERT, not an UPDATE. This also means that you must ensure that you define all necessary columns or you will get unexpected NULL values.

Firstly update it. If affected row count = 0 then insert it. Its the easiest and suitable for all RDBMS.

INSERT OR REPLACE will replace the other fields to default value.

sqlite> CREATE TABLE Book (
  ID     INTEGER PRIMARY KEY AUTOINCREMENT,
  Name   TEXT,
  TypeID INTEGER,
  Level  INTEGER,
  Seen   INTEGER
);

sqlite> INSERT INTO Book VALUES (1001, 'C++', 10, 10, 0);

sqlite> SELECT * FROM Book;
1001|C++|10|10|0

sqlite> INSERT OR REPLACE INTO Book(ID, Name) VALUES(1001, 'SQLite');

sqlite> SELECT * FROM Book;
1001|SQLite|||

If you want to preserve the other field

Method 1

sqlite> SELECT * FROM Book;
1001|C++|10|10|0

sqlite> INSERT OR IGNORE INTO Book(ID) VALUES(1001);
sqlite> UPDATE Book SET Name='SQLite' WHERE ID=1001;

sqlite> SELECT * FROM Book;
1001|SQLite|10|10|0

Method 2

Using UPSERT (syntax was added to SQLite with version 3.24.0 (2018-06-04))

INSERT INTO Book (ID, Name)
  VALUES (1001, 'SQLite')
  ON CONFLICT (ID) DO
  UPDATE SET Name=excluded.Name;

The excluded. prefix equal to the value in VALUES ('SQLite').

Upsert is what you want. UPSERT syntax was added to SQLite with version 3.24.0 (2018-06-04).

CREATE TABLE phonebook2(
  name TEXT PRIMARY KEY,
  phonenumber TEXT,
  validDate DATE
);

INSERT INTO phonebook2(name,phonenumber,validDate)
  VALUES('Alice','704-555-1212','2018-05-08')
  ON CONFLICT(name) DO UPDATE SET
    phonenumber=excluded.phonenumber,
    validDate=excluded.validDate
  WHERE excluded.validDate>phonebook2.validDate;

Be warned that at this point the actual word "UPSERT" is not part of the upsert syntax.

The correct syntax is

INSERT INTO ... ON CONFLICT(...) DO UPDATE SET...

and if you are doing INSERT INTO SELECT ... your select needs at least WHERE true to solve parser ambiguity about the token ON with the join syntax.

Be warned that INSERT OR REPLACE... will delete the record before inserting a new one if it has to replace, which could be bad if you have foreign key cascades or other delete triggers.

If you have no primary key, You can insert if not exist, then do an update. The table must contain at least one entry before using this.

INSERT INTO Test 
   (id, name)
   SELECT 
      101 as id, 
      'Bob' as name
   FROM Test
       WHERE NOT EXISTS(SELECT * FROM Test WHERE id = 101 and name = 'Bob') LIMIT 1;

Update Test SET id='101' WHERE name='Bob';

I believe you want UPSERT.

"INSERT OR REPLACE" without the additional trickery in that answer will reset any fields you don't specify to NULL or other default value. (This behavior of INSERT OR REPLACE is unlike UPDATE; it's exactly like INSERT, because it actually is INSERT; however if what you wanted is UPDATE-if-exists you probably want the UPDATE semantics and will be unpleasantly surprised by the actual result.)

The trickery from the suggested UPSERT implementation is basically to use INSERT OR REPLACE, but specify all fields, using embedded SELECT clauses to retrieve the current value for fields you don't want to change.

I think it's worth pointing out that there can be some unexpected behaviour here if you don't thoroughly understand how PRIMARY KEY and UNIQUE interact.

As an example, if you want to insert a record only if the NAME field isn't currently taken, and if it is, you want a constraint exception to fire to tell you, then INSERT OR REPLACE will not throw and exception and instead will resolve the UNIQUE constraint itself by replacing the conflicting record (the existing record with the same NAME). Gaspard's demonstrates this really well in his answer above.

If you want a constraint exception to fire, you have to use an INSERT statement, and rely on a separate UPDATE command to update the record once you know the name isn't taken.