If you’re getting an error that reads something like ‘currval of sequence “sequence1” is not yet defined in this session‘ when calling the currval() function in PostgreSQL, it’s probably because nextval() hasn’t yet been called for that sequence in the current session.
Object-Relational
Fix “lastval is not yet defined in this session” When Calling the LASTVAL() Function in PostgreSQL
If you’re getting an error that reads something like “lastval is not yet defined in this session” when calling the lastval() function in PostgreSQL, it’s probably because nextval() hasn’t yet been called in the current session.
If you want to avoid this error, only call the lastval() function when you know that nextval() has been called at least once in the current session.
How GENERATE_SERIES() Works in PostgreSQL
In PostgreSQL, we can use the generate_series() function to return a series of values between a given start and stop point. This can be a series of numbers or a series of timestamps.
The function returns a set containing the series.
Fix “START value (…) cannot be less than MINVALUE (…)” When Creating a Sequence in PostgreSQL
If you’re getting an error that reads something like “START value (0) cannot be less than MINVALUE (1)” in PostgreSQL when you’re trying to create a sequence, it’s because your sequence’s start value is lower than its minimum value, when it should be at least the same or higher.
To fix this issue, be sure that the sequence’s start value is at least the same or greater than the minimum value.
How SETVAL() Works in PostgreSQL
In PostgreSQL, we can use the setval() function to set a sequence’s value.
We specify the value when we call the function. We also have the option of setting its is_called flag.
How CURRVAL() Works in PostgreSQL
In PostgreSQL, the currval() function returns the value most recently returned by nextval() for the specified sequence in the current session.
The currval() function is very similar to the lastval() function, except that lastval() doesn’t require the name of a sequence like currval() does. That’s because lastval() doesn’t report on any particular sequence – it reports on the last time nextval() was used in the current session, regardless of which sequence was used. The currval() on the other hand, only reports on the specified sequence.
How LASTVAL() Works in PostgreSQL
In PostgreSQL, the lastval() function returns the value most recently returned by nextval() in the current session.
The lastval() function is very similar to the currval() function, except that lastval() doesn’t require the name of a sequence like currval() does. That’s because lastval() doesn’t report on any particular sequence – it reports on the last time nextval() was used in the current session, regardless of which sequence was used.
How NEXTVAL() Works in PostgreSQL
In PostgreSQL, the nextval() function is used to advance sequence objects to their next value and return that value. We pass the name of the sequence when we call the function. This assumes that the sequence object exists.
Fix “START value (…) cannot be greater than MAXVALUE (…)” When Creating a Sequence in PostgreSQL
If you’re getting an error that reads something like “START value (11) cannot be greater than MAXVALUE (10)” in PostgreSQL when you’re trying to create a sequence, it’s because your sequence’s start value is higher than its maximum value, when it should be lower or the same.
To fix this issue, be sure that the sequence’s maximum value is not less than its start value.
3 PostgreSQL AUTO_INCREMENT Equivalents
In MySQL and MariaDB we can use the AUTO_INCREMENT keyword to create an automatically incrementing column in a table. In SQLite, we’d use the AUTOINCREMENT keyword. And in SQL Server we can use the IDENTITY property. Some of those DBMSs also allow us to create sequence objects, which provide us with more options for creating an auto-increment type column.
When it comes to PostgreSQL, there are a few ways to create an auto-incrementing column. Below are three options for creating an AUTO_INCREMENT style column in Postgres.