Sequences are most commonly used via the serial pseudotype. For example, this command creates both a new table and a new sequence generator, and. In this tutorial, you will learn about PostgreSQL foreign key and how to add foreign keys to tables using foreign key constraints.

Table of Contents 8.1. PostgreSQL has a rich set of native data types available to users. Users can add new types to PostgreSQL using the command. Shows all the built-in general-purpose data types. Most of the alternative names listed in the 'Aliases' column are the names used internally by PostgreSQL for historical reasons. Battery isolator. In addition, some internally used or deprecated types are available, but are not listed here.

Compatibility: The following types (or spellings thereof) are specified by SQL: bigint, bit, bit varying, boolean, char, character varying, character, varchar, date, double precision, integer, interval, numeric, decimal, real, smallint, time (with or without time zone), timestamp (with or without time zone), xml. Each data type has an external representation determined by its input and output functions. Many of the built-in types have obvious external formats. However, several types are either unique to PostgreSQL, such as geometric paths, or have several possible formats, such as the date and time types.

Some of the input and output functions are not invertible, i.e., the result of an output function might lose accuracy when compared to the original input.

If you create a column as serial PostgreSQL automatically creates a sequence for that. The name of the sequence is autogenerated and is always tablename_columnname_seq, in your case the sequence will be names names_id_seq. After inserting into the table, you can call currval() with that sequence name: postgres=> CREATE TABLE names in schema_name (id serial, name varchar(20)); CREATE TABLE postgres=> insert into names (name) values ('Arthur Dent'); INSERT 0 1 postgres=> select currval('names_id_seq'); currval --------- 1 (1 row) postgres=. This is straight from As it was pointed out by @a_horse_with_no_name and @Jack Douglas, currval works only with the current session. So if you are ok with the fact that the result might be affected by an uncommitted transaction of another session, and you still want something that will work across sessions, you can use this: SELECT last_value FROM your_sequence_name; Use the link to SO for more information. From though, it is clearly stated that It is an error to call lastval if nextval has not yet been called in the current session.

So I guess strictly speaking in order to properly use currval or last_value for a sequence across sessions, you would need to do something like that? SELECT setval('serial_id_seq',nextval('serial_id_seq')-1); Assuming, of course, that you will not have an insert or any other way of using the serial field in the current session. I had to do this when I was hard-coding primary keys for generated fixture data where I wanted the PK values that would normally be generated incrementally to be determined ahead of time to make client testing easier. In order to support inserts when doing that on a column that is normally governed by the default value from a nextval() you then have to manually set the sequence to match the number of fixture records you inserted with the hardcoded IDs. Also, the way to solve for the problem of currval() / lastval() not being available pre-nextval is to just SELECT on the sequence directly. – Sep 19 '16 at 17:07 •.

So there are some issues with these various methods: Currval only gets the last value generated in the current session - which is great if you don't have anything else generating values, but in cases where you might call a trigger and/or have the sequence advanced more than once in the current transaction it's not going to return the correct value. That's not an issue for 99% of the people out there - but it's something that one should take into consideration. Scales for jazz improvisation pdf. The best way to get the unique identifier assigned after an insert operation is using the RETURNING clause.