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.
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.
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.
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.
PostgreSQL allows us to create sequence objects, otherwise known as “sequence generators”, or simply “sequences”. As the name suggests, a sequence object is used to generate sequence numbers.
We can use sequences to generate incrementing numbers or decrementing numbers.
In PostgreSQL we can create auto-incrementing columns using the serial data type. The serial type causes the column to be automatically populated with an auto-incrementing value each time a new row is inserted. The same applies for the smallserial and bigserial types.
This article provides an overview of how these data types work.
PostgreSQL provides us with several options when it comes to cloning a table. Below are six methods we can use to clone a table in Postgres. The method we use will depend on things like, whether or not we want to transfer the data, indexes, etc.
When working with SQL, we can use the INSERT statement to insert a new row into a table. But what if we want to insert more than one row?
Fortunately, we can still use the INSERT statement. Below is a quick example that inserts multiple rows using SQL.