DB 101: PostgreSQL, MySQL and SQLite compared

2012-08-06 ·

In this post I go through basic adminstrative commands for PostgreSQL, MySQL and SQLite. The idea is to organize it in one place as it slips my mind quite often. In square brackets I'm putting optional parameters. For Linux I assume a root access.

Installing

PostgreSQL

On OSX

λ brew install postgres

On Linux (+ setting a possword for postgres user)

λ apt-get install postgresql
λ passwd postgres

MySQL

On OSX

λ brew install mysql

On Linux

λ apt-get install mysql-server mysql-client

Accessing a DB server

PostgreSQL

λ su - postgres
λ psql dbname

MySQL

λ mysql -u root -p [dbname]

Creating a DB user

PostgreSQL

On OSX

λ createuser zaiste
Shall the new role be a superuser? (y/n) n
Shall the new role be allowed to create databases? (y/n) y
Shall the new role be allowed to create more new roles? (y/n) n

On Linux

λ sudo -u postgres createuser zaiste
Shall the new role be a superuser? (y/n) n
Shall the new role be allowed to create databases? (y/n) y
Shall the new role be allowed to create more new roles? (y/n) n

With psql

=# create user zaiste with password 'pass';
CREATE ROLE

MySQL

mysql> CREATE USER 'zaiste'@'localhost' IDENTIFIED BY 'pass';

Creating a database

PostgreSQL

On CLI

λ createdb realm -O zaiste

With psql

=# create database realm with owner zaiste;
CREATE DATABASE

MySQL

mysql> CREATE DATABASE realm;

On localhost

mysql> GRANT ALL ON realm.* TO zaiste@localhost [identified by 'pass'];

On specific IP

mysql> GRANT ALL ON realm.* TO zaiste@192.168.1.5 [identified by 'pass'];

SQLite

In SQLite3 there is no database server. Databases are just regular files. If the file doesn't exist, it will be created once you launch the sqlite client.

λ sqlite realm.db

Check Version

PostgreSQL

=# select version();
                                  version
------------------------------------------------------------------------------
 PostgreSQL 9.2.0 on x86_64-apple-darwin12.1.0, compiled by Apple clang version
    4.0 (tags/Apple/clang-421.0.57) (based on LLVM 3.1svn), 64-bit

MySQL

More details:

λ mysqladmin -u root -p -h localhost version
Enter password:
mysqladmin  Ver 8.42 Distrib 5.1.61, for debian-linux-gnu on x86_64
Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Server version          5.1.61-0ubuntu0.11.10.1
Protocol version        10
Connection              Localhost via UNIX socket
UNIX socket             /var/run/mysqld/mysqld.sock
Uptime:                 77 days 12 hours 15 min 42 sec

Threads: 1  Questions: 70715217  Slow queries: 2  Opens: 40905  Flush tables: 1
   Open tables: 64  Queries per second avg: 10.559

Less details:

λ  mysql -V
mysql  Ver 14.14 Distrib 5.1.61, for debian-linux-gnu (x86_64) using readline 6.2

Check Socket

MySQL

λ mysqladmin -u root variables | grep socket

Importing

PostgreSQL

λ mysql -u zaiste -p -h localhost dbname < dumpfile.sql

Listing Databases

PostgreSQL

=# \l[ist]
                             List of databases
   Name     | Owner  | Encoding |   Collate   |    Ctype    | Access privileges
------------+--------+----------+-------------+-------------+-------------------
 postgres   | zaiste | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0  | zaiste | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/zaiste        +
            |        |          |             |             | zaiste=CTc/zaiste
 template1  | zaiste | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/zaiste        +
            |        |          |             |             | zaiste=CTc/zaiste
 realm      | zaiste | UTF8     | en_US.UTF-8 | en_US.UTF-8 |

MySQL

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| realm              |
| db1                |
| db2                |
+--------------------+

SQLite

.databases

Switch database

PostgreSQL

=# \c[onnect] db1;
You are now connected to database "db1" as user "zaiste".

MySQL

mysql> use db1;
Database changed

Showing tables

PostgreSQL

realm=# \d[t]
            List of relations
 Schema |       Name        | Type     | Owner
--------+-------------------+----------+--------
 public | table1            | table    | zaiste
 public | table1_id_seq     | sequence | zaiste
 public | table2            | table    | zaiste
 public | table2_id_seq     | sequence | zaiste
 public | table3            | table    | zaiste
 public | table3_id_seq     | sequence | zaiste

MySQL

mysql> show tables;
+-------------------+
| Tables_in_realm   |
+-------------------+
| table1            |
| table2            |
| table3            |
+-------------------+

SQLite

.tables

Showing schema

PostgreSQL

=# \d table1
                            Table "public.table1"
 Column|    Type                |                  Modifiers
-------+------------------------+----------------------------------------------------
 id    | integer                | not null default nextval('table1_id_seq'::regclass)
 name  | character varying(255) |
 title | character varying(255) |

MySQL

mysql> describe table1;
+--------------------+--------------+------+-----+---------+----------------+
| Field              | Type         | Null | Key | Default | Extra          |
+--------------------+--------------+------+-----+---------+----------------+
| id                 | int(11)      | NO   | PRI | NULL    | auto_increment |
| sequence           | int(11)      | YES  |     | NULL    |                |
| name               | varchar(255) | YES  |     | NULL    |                |
| title              | varchar(255) | YES  |     | NULL    |                |
+--------------------+--------------+------+-----+---------+----------------+

SQLite

.schema table1

Setting password

MySQL

For the first time

λ mysqladmin -u root -p password NEWPASS

Updating the password

λ mysqladmin -u root -p'OLDPASS' password NEWPASS

Timing

PostgreSQL

=# \timing
Timing is on.

=# SELECT * from pg_catalog.pg_attribute ;
Time: 9.583 ms
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