The AUTOINCREMENT keyword imposes extra CPU, memory, disk space, andĭisk I/O overhead and should be avoided if not strictly needed. However if 9223372036854775807 has been used then an SQLITE_FULL error will be raised. With AUTOINCREMENT the algorithm takes the higher value of the maximum value and a value stored in the table sqlite_sequence for the respective table and uses that (thus any deleted higher valueswill not be re-used). Unless that value exceeds 9223372036854775807 in which case SQlite will make some attempts to find an unused lower value (normally between 372036854775807). That is without AUTOINCREMENT the value generated for the rowid column will find the maximum value in the table and increment it. I have a column named id in my SQLite database which is auto-increment, Primary Key, Unique. Next, insert a record into this table, passing a null value into the SQLite autoincrement field: sqlite> INSERT INTO salespeople VALUES (null, 'Fred', 'Flinstone', 10.0) Now, just use the SQLite lastinsertrowid () function to get the value of the SQLite autoincrement field that was just generated: sqlite> select lastinsertrowid () 2. it could alternatively use SET mycolumn 'myprefix'rowid.
The TRIGGER is actioned whenever a row is inserted and in this case it mimics what the SQLite auto-generation of the rowid value does prefixing the value. So an AUTOINCREMENT column is an alias of the rowid column and uses a differnt, more expensive algorithm than an alias of the rowid without AUTOINCREMENT. This creates a table along with a TRIGGER and then inserts the same data as above. I have a column named id in my SQLite database which is auto-increment, Primary Key, Unique. The rowid is what is indexed, and is basically the most primary index and the most efficient, which always exists unless the table is defined using the WITHOUT ROWID keyword. Since it is auto increment, the data is already sorted by that column in ascending order.
That is, all AUTOINCREMENT does is add a constraint that requires the value assigned to the column to be higher than any existing value, or higher than any value that has been used, in that column.īut there's more to it than that it is your_column INTEGER PRIMARY KEY (AUTOINCREMENT can only be used on such a column and there can only be 1 such column per table) makes that column an alias of the hidden rowid column. I am using auto increment on an integer data column in SQLite. Make sure you know what you are doing before you undertake such changes.
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