MacLochlainns Weblog

The process of creating a schema requires you grant the CREATE ON DATABASE privilege to the user as the postgres user. You use the following syntax:

GRANT CREATE ON DATABASE videodb TO student;

As the student user, you create the app schema with the following syntax:

CREATE SCHEMA app;

Then, you can query the result as follows:

SELECT   * 
FROM     pg_catalog.pg_namespace
ORDER BY nspname;

You should see the following:

      nspname       | nspowner |               nspacl                
--------------------+----------+-------------------------------------
 app                |    16390 | 
 information_schema |       10 | {postgres=UC/postgres,=U/postgres}
 pg_catalog         |       10 | {postgres=UC/postgres,=U/postgres}
 pg_temp_1          |       10 | 
 pg_toast           |       10 | 
 pg_toast_temp_1    |       10 | 
 public             |       10 | {postgres=UC/postgres,=UC/postgres}
(7 rows)

If you create a revision_history table without a schema name, it is automatically placed in the public schema, which means an attempt to describe the table will return an error. For example, you create a revision_history table with the following command:

CREATE TABLE app.revision_history
( revision_history_id serial
, session_id          VARCHAR
, TABLE_NAME          VARCHAR
, revision_id         INTEGER );

You describe the revision_history table with the following command:

\d revision_history

It will show the following because there is no revision_history table in the public schema and the default search path only include a schema that shares the name with the student user and the public schema.

Did not find any relation named "revision_history".

You can show the search path with the following:

show search_path;

It should return the following, which is a schema that shares the user’s name and public.

   search_path   
-----------------
 "$user", public
(1 row)

You set the search path as follows:

SET search_path TO app, "$user", public;

After you set the search_path, a standard attempt to describe the table will find the table whether it is in the app or public schema. That means the following command:

\d revision_history

Shows:

                                                  Table "app.revision_history"
       Column        |       Type        | Collation | Nullable |                            Default                            
---------------------+-------------------+-----------+----------+---------------------------------------------------------------
 revision_history_id | integer           |           | not null | nextval('revision_history_revision_history_id_seq'::regclass)
 session_id          | character varying |           |          | 
 table_name          | character varying |           |          | 
 revision_id         | integer           |           |          |

As always, I hope this helps somebody looking for an answer.

Just sorting out how to query the information_schema to discover the magic for a query of a table’s foreign key constraints. This query works to return the foreign key constraints:

SELECT   conrelid::regclass::text AS table_from
,        conname AS foreign_key
,        pg_get_constraintdef(oid)
FROM     pg_constraint
WHERE    contype = 'f'
AND      connamespace = 'public'::regnamespace 
AND      conrelid::regclass::text = 'rental_item'
ORDER BY conrelid::regclass::text
,        conname;

It returns the following for the rental_item table:

 table_from  |   foreign_key    |                           pg_get_constraintdef                            
-------------+------------------+---------------------------------------------------------------------------
 rental_item | fk_rental_item_1 | FOREIGN KEY (rental_id) REFERENCES rental(rental_id)
 rental_item | fk_rental_item_2 | FOREIGN KEY (item_id) REFERENCES item(item_id)
 rental_item | fk_rental_item_3 | FOREIGN KEY (created_by) REFERENCES system_user(system_user_id)
 rental_item | fk_rental_item_4 | FOREIGN KEY (last_updated_by) REFERENCES system_user(system_user_id)
 rental_item | fk_rental_item_5 | FOREIGN KEY (rental_item_type) REFERENCES common_lookup(common_lookup_id)
(5 rows)

As always, I post these tidbit for others to discover and use with less pain.

I’m migrating my database classes from the Oracle database to the PostgreSQL database. Using the Oracle Express Edition has always required a virtualized image because students use Windows and Mac OS. Also, the university doesn’t like my use of a virtualized image. Virtualization imposes incremental cost on students to have high end laptops.

The available Docker images don’t typically support the Oracle Express Edition. That means there are licensing implications tied to Oracle.

As a committee, we decided to use PostgreSQL as our new database platform. We opted to use PostgreSQL over MySQL because it supports arrays and stored procedures. PostgreSQL PL/pgSQL are a solid implementation of stored procedures. While MySQL supports a stored procedure language, it effectively discourages using it.

We use sqlplus, mysql, or psql Command-Line Interface (CLI) as the primary interface. That’s because CLI supports production-oriented deployment and DevOps practices. The Open Source DBeaver project provides a clean native GUI management console for PostgreSQL. DBeaver also supports other databases, which pgAdmin doesn’t.

You click the Download button from the DBeaver home page. It support Windows, Mac OS, and Linux distributions. I downloaded the Linux RPM package to my Downloads directory. You can run the RPM with the following syntax:

rpm -ivh dbeaver-ce-6.2.3-stable.x86_64.rpm

It doesn’t check for dependencies. The installation is quick. You can verify that it’s installed with the following command:

which dbeaver

It installs here:

/usr/bin/dbeaver

If you failed to install the PostgreSQL JAR file, you’ll see the following error message:

It will look like the following on Linux:

You should have a user in the pg_hba.conf file, like the following:

host    all             all             127.0.0.1/32            trust

As always, I hope this helps those solving problems.

Installing PostgreSQL 11 on Fedora, Version 30, requires an update to my previous instructions to create a sandboxed user. A sandboxed user can only access a non-data dictionary database with a password. In the real world, rather than a personal test instance you would configure users to include aspects of networking. However, this post is only showing you how to connect from the local server.

This post builds on my PostgreSQL Installation blog post and shows you how to create a tablespace, database, role, and user. It also shows you how to change the default configuration for how users connect to the database.

The following steps create a tablespace, database, role, and user:

1. Create tablespace

postgres=# show data_directory;

     data_directory     
------------------------
 /var/lib/pgsql/11/data
(1 row)

mkdir videoDB

2. Create Tablespace

CREATE TABLESPACE video_db
  OWNER postgres
  LOCATION '/var/lib/pgsql/11/videoDB';

CREATE TABLESPACE

SELECT * FROM pg_tablespace;

  spcname   | spcowner | spcacl | spcoptions 
------------+----------+--------+------------
 pg_default |       10 |        | 
 pg_global  |       10 |        | 
 video_db   |       10 |        | 
(3 rows)

3. Create a Database

CREATE DATABASE videodb
  WITH OWNER = postgres
       ENCODING = 'UTF8'
       TABLESPACE = video_db
       LC_COLLATE = 'en_US.UTF-8'
       LC_CTYPE = 'en_US.UTF-8'
       CONNECTION LIMIT = -1;

postgres# \l

                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 videodb   | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =Tc/postgres         +
           |          |          |             |             | postgres=CTc/postgres+
           |          |          |             |             | dba=CTc/postgres
(4 rows)

COMMENT ON DATABASE videodb IS 'Video Database';

4. Create a Role, Grant, and User

5. Connect to the videodb as the student user

psql -d videodb -U student -W

psql (11.4, server 11.5)
Type "help" for help.
 
videodb=>

SELECT current_database();

 current_database 
------------------
 videodb
(1 row)

This has shown you how to create a videodb database, dba role, and student user.

Installing PostreSQL 11 on Fedora 30 wasn’t straight forward but there were some instructions that helped. The first step requires you to update the yum repository, like this as the root user:

rpm -Uvh https://yum.postgresql.org/11/fedora/fedora-30-x86_64/pgdg-fedora-repo-latest.noarch.rpm

Then, you install the PostgreSQL with this command as the root user:

dnf install postgresql11-server

After installing the PostreSQL Server I got a few errors with the symbolic links failing to resolve in the log files. Then, I realized they only failed to create symbolic links because the fresh installation deploys executables directly to the /usr/bin directory.

Retrieving https://yum.postgresql.org/11/fedora/fedora-30-x86_64/pgdg-fedora-repo-latest.noarch.rpm
warning: /var/tmp/rpm-tmp.MD4lRU: Header V4 DSA/SHA1 Signature, key ID 442df0f8: NOKEY
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
Updating / installing...
   1:pgdg-fedora-repo-42.0-4          ################################# [100%]
[root@localhost ~]# dnf install postgresql11-server
PostgreSQL 11 30 - x86_64                                                         215 kB/s | 585 kB     00:02    
PostgreSQL 10 30 - x86_64                                                         199 kB/s | 541 kB     00:02    
PostgreSQL 9.6 30 - x86_64                                                        295 kB/s | 515 kB     00:01    
PostgreSQL 9.5 30 - x86_64                                                        179 kB/s | 495 kB     00:02    
PostgreSQL 9.4 30 - x86_64                                                        269 kB/s | 469 kB     00:01    
Last metadata expiration check: 0:00:01 ago on Mon 19 Aug 2019 02:25:56 AM MDT.
Dependencies resolved.
==================================================================================================================
 Package                           Architecture         Version                        Repository            Size
==================================================================================================================
Installing:
 postgresql11-server               x86_64               11.5-1PGDG.f30                 pgdg11               4.8 M
Installing dependencies:
 postgresql11                      x86_64               11.5-1PGDG.f30                 pgdg11               1.7 M
 postgresql11-libs                 x86_64               11.5-1PGDG.f30                 pgdg11               374 k
 
Transaction Summary
==================================================================================================================
Install  3 Packages
 
Total download size: 6.9 M
Installed size: 32 M
Is this ok [y/N]: y
Downloading Packages:
(1/3): postgresql11-libs-11.5-1PGDG.f30.x86_64.rpm                                213 kB/s | 374 kB     00:01    
(2/3): postgresql11-11.5-1PGDG.f30.x86_64.rpm                                     698 kB/s | 1.7 MB     00:02    
(3/3): postgresql11-server-11.5-1PGDG.f30.x86_64.rpm                              1.5 MB/s | 4.8 MB     00:03    
------------------------------------------------------------------------------------------------------------------
Total                                                                             2.2 MB/s | 6.9 MB     00:03     
warning: /var/cache/dnf/pgdg11-cde8ad453ae6cd5b/packages/postgresql11-11.5-1PGDG.f30.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID 442df0f8: NOKEY
PostgreSQL 11 30 - x86_64                                                         1.6 MB/s | 1.7 kB     00:00    
Importing GPG key 0x442DF0F8:
 Userid     : "PostgreSQL RPM Building Project <pgsqlrpms-hackers@pgfoundry.org>"
 Fingerprint: 68C9 E2B9 1A37 D136 FE74 D176 1F16 D2E1 442D F0F8
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG
Is this ok [y/N]: y
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                          1/1 
  Installing       : postgresql11-libs-11.5-1PGDG.f30.x86_64                                                  1/3 
  Running scriptlet: postgresql11-libs-11.5-1PGDG.f30.x86_64                                                  1/3 
  Installing       : postgresql11-11.5-1PGDG.f30.x86_64                                                       2/3 
  Running scriptlet: postgresql11-11.5-1PGDG.f30.x86_64                                                       2/3 
failed to link /usr/bin/psql -> /etc/alternatives/pgsql-psql: /usr/bin/psql exists and it is not a symlink
failed to link /usr/bin/clusterdb -> /etc/alternatives/pgsql-clusterdb: /usr/bin/clusterdb exists and it is not a symlink
failed to link /usr/bin/createdb -> /etc/alternatives/pgsql-createdb: /usr/bin/createdb exists and it is not a symlink
failed to link /usr/bin/createuser -> /etc/alternatives/pgsql-createuser: /usr/bin/createuser exists and it is not a symlink
failed to link /usr/bin/dropdb -> /etc/alternatives/pgsql-dropdb: /usr/bin/dropdb exists and it is not a symlink
failed to link /usr/bin/dropuser -> /etc/alternatives/pgsql-dropuser: /usr/bin/dropuser exists and it is not a symlink
failed to link /usr/bin/pg_dump -> /etc/alternatives/pgsql-pg_dump: /usr/bin/pg_dump exists and it is not a symlink
failed to link /usr/bin/pg_dumpall -> /etc/alternatives/pgsql-pg_dumpall: /usr/bin/pg_dumpall exists and it is not a symlink
failed to link /usr/bin/pg_restore -> /etc/alternatives/pgsql-pg_restore: /usr/bin/pg_restore exists and it is not a symlink
failed to link /usr/bin/reindexdb -> /etc/alternatives/pgsql-reindexdb: /usr/bin/reindexdb exists and it is not a symlink
failed to link /usr/bin/vacuumdb -> /etc/alternatives/pgsql-vacuumdb: /usr/bin/vacuumdb exists and it is not a symlink
 
  Running scriptlet: postgresql11-server-11.5-1PGDG.f30.x86_64                                                3/3 
  Installing       : postgresql11-server-11.5-1PGDG.f30.x86_64                                                3/3 
  Running scriptlet: postgresql11-server-11.5-1PGDG.f30.x86_64                                                3/3 
  Verifying        : postgresql11-11.5-1PGDG.f30.x86_64                                                       1/3 
  Verifying        : postgresql11-libs-11.5-1PGDG.f30.x86_64                                                  2/3 
  Verifying        : postgresql11-server-11.5-1PGDG.f30.x86_64                                                3/3 
 
Installed:
  postgresql11-server-11.5-1PGDG.f30.x86_64                   postgresql11-11.5-1PGDG.f30.x86_64                  
  postgresql11-libs-11.5-1PGDG.f30.x86_64                    
 
Complete!

After installing the PostgreSQL Server 11, you need to initialize the database. You use the following command to initialize the database as the root user:

/usr/pgsql-11/bin/postgresql-11-setup initdb

It should return the following:

Initializing database ... OK

The PostgreSQL Server 11 database installs in the /var/lib/pgsql/11/data directory. You can list the contents, which should mirror these:

drwx------. 5 postgres postgres  4096 Aug 19 02:45 base
drwx------. 2 postgres postgres  4096 Aug 19 02:45 global
drwx------. 2 postgres postgres  4096 Aug 19 02:45 log
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_commit_ts
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_dynshmem
-rw-------. 1 postgres postgres  4269 Aug 19 02:45 pg_hba.conf
-rw-------. 1 postgres postgres  1636 Aug 19 02:45 pg_ident.conf
drwx------. 4 postgres postgres  4096 Aug 19 02:45 pg_logical
drwx------. 4 postgres postgres  4096 Aug 19 02:45 pg_multixact
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_notify
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_replslot
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_serial
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_snapshots
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_stat
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_stat_tmp
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_subtrans
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_tblspc
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_twophase
-rw-------. 1 postgres postgres     3 Aug 19 02:45 PG_VERSION
drwx------. 3 postgres postgres  4096 Aug 19 02:45 pg_wal
drwx------. 2 postgres postgres  4096 Aug 19 02:45 pg_xact
-rw-------. 1 postgres postgres    88 Aug 19 02:45 postgresql.auto.conf
-rw-------. 1 postgres postgres 23895 Aug 19 02:45 postgresql.conf

You need to enable and start the postgresql-11.service with the following commands as the root user:

systemctl enable postgresql-11.service
systemctl start postgresql-11.service

You can login to test the configuration as the root user, like this:

su - postgres -c "psql"

You will see something like this:

psql: /usr/pgsql-11/lib/libpq.so.5: no version information available (required by psql)
psql: /usr/pgsql-11/lib/libpq.so.5: no version information available (required by psql)
psql (11.4, server 11.5)
Type "help" for help.
 
postgres=#

The error message appear to indicate there’s a bug (at least Bug #15798 is similar). Specifically, a missing function in the libya.so.5 library. Determining that impact took some time because of what else I had in the queue.

The Bug (at least Bug #15798 gave part of the fix. The problem was figuring out where the LD_LIBRARY_PATH should really be set, and I sorted that out.

If you inspect the postgres home directory (/var/lib/pgsql), you’ll find the following .bash_profile file:

[ -f /etc/profile ] && source /etc/profile
PGDATA=/var/lib/pgsql/11/data
export PGDATA
# If you want to customize your settings,
# Use the file below. This is not overridden
# by the RPMS.
[ -f /var/lib/pgsql/.pgsql_profile ] && source /var/lib/pgsql/.pgsql_profile

Then, you create the .pgsql_profile file in that directory. You should put the following command in the file:

export set LD_LIBRARY_PATH=/usr/lib64 needle < /dev/null

Then, when you login as the postgres user:

psql -U postgres

You will see:

psql (11.4, server 11.5)
Type "help" for help.
 
postgres=#

or, you can login to test the configuration as the root user with the syntax used earlier:

su - postgres -c "psql"

You need to put the LD_LIBRARY_PATH environment variable in the .bashrc of users who will access the PostgreSQL 11 database.

As always, I hope this helps those working it from the ground up.

Somebody asked: How do you run a script file from PostgreSQL’s psql prompt? I created two files to answer the question. Here are the two files:

Static File

SELECT 'Hello World!';

Dynamic File

SELECT 'Hello ['||current_user||']!';

It’s a simple solution, you put a \i or \include before the script file name, like:

\i helloworld.sql

It outputs:

   ?column?   
--------------
 Hello World!

or

\include hellowhom.sql

It outputs:

     ?column?     
------------------
 Hello [student]!

I hope this helps those trying to call SQL script files from an interactive psql session.

PostgreSQL like Oracle supports record data types but unlike Oracle, PostgreSQL doesn’t support collections of record data types. Here’s an example of how to define a PostgreSQL composite data type, and how to use it as a column’s data type.

CREATE TYPE address_type AS
( street_address  VARCHAR
, city            VARCHAR
, state           VARCHAR
, zip_code        VARCHAR );

Then, you define an ADDRESS table, like:

CREATE TABLE address
( address_id      SERIAL
, address_struct  ADDRESS_TYPE );

You can now insert rows like:

-- Insert the first row.
INSERT INTO address
( address_struct )
VALUES
(('52 Hubble Street','Lexington','KY','40511-1225'));
 
-- Insert the second row.
INSERT INTO address
( address_struct )
VALUES
(('54 Hubble Street','Lexington','KY','40511-1225'));

Then, you can query them like this:

SELECT * FROM address;

It returns:

 address_id |                address_struct
------------+----------------------------------------------
          1 | ("52 Hubble Street",Lexington,KY,40511-1225)
          2 | ("54 Hubble Street",Lexington,KY,40511-1225)
(2 rows)

You must use parentheses around the ADDRESS_STRUCT column to query individual items, like:

SELECT   address_id
,       (address_struct).street_address
,       (address_struct).city
,       (address_struct).state
,       (address_struct).zip_code
FROM     address;

It returns output like a table:

 address_id |  street_address  |   city    | state |  zip_code
------------+------------------+-----------+-------+------------
          1 | 52 Hubble Street | Lexington | KY    | 40511-1225
          2 | 54 Hubble Street | Lexington | KY    | 40511-1225
(2 rows)

While you can define a table that holds an array of a composite type, there’s no syntax that appears to work with an array of a composite type. I hope this helps those interested in implementing record structures in PostgreSQL.

PostgreSQL’s approach to automatic numbering is as simple as Oracle but different than MySQL, and Microsoft SQL Server. For example, you have a two-step process with Oracle, PostgreSQL, MySQL, and Microsoft SQL Server. First, you create an Oracle table with the GENERATED AS IDENTITY clause, a PostgreSQL table with the SERIAL data type, a MySQL table with the AUTO_INCREMENT clause, and a Microsoft SQL Server table with the IDENTITY(1,1) clause. Then, you need to write an INSERT statement for Oracle, MySQL, or Microsoft SQL Server like:

1. Oracle’s INSERT statement excludes the auto-incrementing column from the list of columns or provides a NULL value in the VALUES-list. You can then assign the RETURNING INTO result from an INSERT statement to a session-level (bind) variable.
2. MySQL’s INSERT statement excludes the auto-incrementing column from the list of columns or provides a NULL value in the VALUES-list. You can then assign the LAST_INSERT_ID() function value to a session-level variable, and populate a foreign key column.
3. Microsoft SQL Server’s INSERT statement excludes the auto-incrementing column from the list of columns or provides a NULL value in the VALUES-list. You can then assign the SCOPE_IDENTITY() function’s value to a session-level variable, and populate a foreign key column.

PostgreSQL differs because it works differently between the SQL and PL/pgSQL contexts. Let’s look at how you link the insert of data into two tables in both contexts.

The following PostgreSQL syntax creates an ADDRESS table with an auto incrementing ADDRESS_ID column that uses a SERIAL data type, which acts like an auto numbering column:

/* Create a customer table. */
CREATE TABLE customer
( customer_id     SERIAL CONSTRAINT customer_pk PRIMARY KEY
, first_name      VARCHAR(20)
, last_name       VARCHAR(20));
 
/* Create an address table. */
CREATE TABLE address
( address_id      SERIAL CONSTRAINT address_pk PRIMARY KEY
, customer_id     INTEGER
, street_address  VARCHAR(40)
, city            VARCHAR(30)
, state           VARCHAR(8)
, zip_code        VARCHAR(10));

If you want to insert one row into the CUSTOMER table and a related row in the ADDRESS table. You have two possible approaches. One works in both the SQL and PL/pgSQL contexts. That mechanism requires you to use a scalar subquery to capture the foreign key value of the CUSTOMER_ID column in the ADDRESS table, like this:

/* Insert into customer table. */
INSERT INTO customer
( first_name, last_name ) 
VALUES
('F. Scott','Fitzgerald');
 
/* Insert into address table. */
INSERT INTO address
( customer_id
, street_address
, city
, state
, zip_code )
VALUES
((SELECT   customer_id
  FROM     customer
  WHERE    first_name = 'F. Scott'
  AND      last_name = 'Fitzgerald')
,'599 Summit Avenue'
,'St. Paul'
,'Minnesota'
,'55102');

The RETURNING INTO clause of PostgreSQL only works in a PL/pgSQL context, like this:

DO $$
DECLARE lv_customer_id INTEGER;
BEGIN
  /* Insert into customer table. */
  INSERT INTO customer
  ( first_name, last_name ) 
  VALUES
  ('Madeleine','Smith') 
  RETURNING customer_id INTO lv_customer_id;
 
  /* Insert into address table. */
  INSERT INTO address
  ( customer_id
  , street_address
  , city
  , state
  , zip_code )
  VALUES
  ( lv_customer_id
  ,'7 Blythswood Square'
  ,'Glasgow'
  ,'Scotland'
  ,'G2 4BG');
 
  /* Manage any exceptions. */
  EXCEPTION
    WHEN OTHERS THEN
      RAISE NOTICE '% %', SQLERRM, SQLSTATE;
END$$;

You query the auto generated values and data from the INSERT statement to the CUSTOMER table with a scalar subquery against the natural key (the FIRST_NAME and LAST_NAME columns) from the ADDRESS table. The following is an example of such a query:

SELECT   *
FROM     customer c INNER JOIN address a
ON       c.customer_id = a.customer_id;

It returns:

 customer_id | first_name | last_name  | address_id | customer_id |   street_address    |   city   |   state   | zip_code
-------------+------------+------------+------------+-------------+---------------------+----------+-----------+----------
           1 | F. Scott   | Fitzgerald |          1 |           1 | 599 Summit Avenue   | St. Paul | Minnesota | 55102
           2 | Madeleine  | Smith      |          2 |           2 | 7 Blythswood Square | Glasgow  | Scotland  | G2 4BG
(2 rows)

My take is that the RETURNING column_value INTO local_value clause is a better approach than using Oracle’s .NEXTVAL and .CURRVAL values. I also think the RETURNING INTO clause is a better approach than using MySQL’s LAST_INSERT_ID() or Microsoft SQL Server’s SCOPE_IDENTITY().

Initially, I felt it was odd that the PostgreSQL disallows the RETURNING INTO clause in a SQL context, because it allows the syntax in a PL/pgSQL context. After some reflection the choice makes more sense because most developers work within a procedural context when they use transactions across two or more tables. PL/pgSQL is PostgreSQL’s procedural context from managing transactions across two or more tables.

As always, I hope this helps.

How time flies, last March I explained how to install and configure PostgreSQL on Windows. It was my intent to start posting more content on PostgreSQL but I was distracted by another writing commitment on Oracle Database 12c PL/SQL Advanced Programming Techniques, which should be available in November. It tempted me away from PostgreSQL because I got to write about how to use Java inside Oracle Database 12c, which was fun. Having completed that, I’m back on task. Here’s the second entry on PostgreSQL. It shows you howto create your own database, database administrator role, user, and how to connect with psql CLI (Command Line Interface) as the new user.

1. Create a user-defined video_db tablespace for your database. This requires that you know where the physical files where created when you installed PostgreSQL. You can discover the directory with the following query:

SELECT   setting AS "Data Location"
FROM     pg_settings
WHERE    name = 'data_directory';

            Data Location
--------------------------------------
 C:/Program Files/PostgreSQL/9.3/data
(1 row)

CREATE TABLESPACE video_db
  OWNER postgres
  LOCATION 'C:\Program Files\PostgreSQL\9.3\data';

SELECT * FROM pg_tablespace;

  spcname   | spcowner | spcacl | spcoptions
------------+----------+--------+------------
 pg_default |       10 |        |
 pg_global  |       10 |        |
 video_db   |       10 |        |
(3 rows)

2. Create a database that uses your user-defined video_db tablespace with the following two commands:

CREATE DATABASE videodb
  WITH OWNER = postgres
       ENCODING = 'UTF8'
       TABLESPACE = video_db
       LC_COLLATE = 'English_United States.1252'
       LC_CTYPE = 'English_United States.1252'
       CONNECTION LIMIT = -1;
 
COMMENT ON DATABASE videodb
  IS 'VideoDB';

3. Create a database role, grant the super user privileges to the role, and create a user with the role. You can do that with the following three commands:

CREATE ROLE dba
  WITH SUPERUSER;
 
GRANT ALL PRIVILEGES ON DATABASE videodb TO dba;
 
CREATE USER video
  WITH ROLE dba
       PASSWORD 'video';

4. Connect to the new videodb database with the psql CLI as the video user. You can do that with the following OS command:

psql -d videodb -U video

5. Once connected as the new video user, you can use a system information function to determine the current database:

SELECT current_database();

 current_database
------------------
 videodb
(1 row)

There are many privilege options, and you should choose wisely which ones you use. As always, I hope this answers questions for other users.