I did not know what the database did and I deleted it without realizing that now I wouldn't be able to run psql again. How do I get thngs back to normal again?
The postgres database isn't really needed.
But you can re-create it using:
psql -U postgres -d template1
psql (13.1)
postgres=# create database postgres;
The -d template1 tells psql to connect to the template1 database.
Related
I try to create a database. After reading around, I saw two methods:
Method 1:
xxxxxx:~$ sudo -i -u postgres
postgres$xxxx:~$ createdb mydb1
Method 2:
xxxxxx:~$ sudo -u postgres psql
postgres:# CREATE DATABASE mydb2
If I do method 1, the database mydb1 gets created. And when I am in postgres:# and do this \list, I can see mydb1 being listed.
However, if I do method 2, after the end line above, there is no error whatsoever. But when I do \list in postgres:#, I don't the database mydb2 being listed.
My first time trying to set up a postgresql database. Please, if someone could explain what is going on.
In psql you need to end the sql with the semicolon:
create database mydb2;
I'm failing at adding a new DB role, that would have a SELECT privilege on tables from particular database.
My problem is that the role is not able to SELECT from a table in existing DB.
Here's my failing test case (written so it can safely be copy-pasted into a /tmp/test.sh and executed):
# --- cleanup objects, if any
psql -U postgres -c "REVOKE SELECT ON ALL SEQUENCES IN SCHEMA public FROM db_reader"
psql -U postgres -c "REVOKE SELECT ON ALL TABLES IN SCHEMA public FROM db_reader"
psql -U postgres -c "REVOKE USAGE ON SCHEMA public FROM db_reader"
psql -U postgres -c "DROP ROLE IF EXISTS db_reader"
psql -U postgres -c "DROP DATABASE IF EXISTS some_existing_db"
# --- test
psql -U postgres -c "CREATE DATABASE some_existing_db"
psql -U postgres some_existing_db -c "CREATE TABLE cats (name varchar(10))"
psql -U postgres some_existing_db -c "INSERT INTO cats (name) VALUES ('a'), ('b')"
psql -U postgres -c "CREATE ROLE db_reader WITH login"
psql -U postgres -c 'GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO db_reader'
psql -U postgres -c 'GRANT SELECT ON ALL TABLES IN SCHEMA public TO db_reader'
psql -U postgres -c 'GRANT USAGE ON SCHEMA public TO db_reader'
psql -U db_reader some_existing_db -c "SELECT COUNT(1) FROM cats"
Looks like I'm missing something extremely, embarrassingly obvious here, as the above fails with the following error:
ERROR: permission denied for relation cats
Why?
You are missing that databases are logically separated.
Your GRANT statements are executed in database postgres (if you do not specify a database name, psql will try to connect to a database with the same name as the database user).
Consequently, the effect of these grants is limited to the database to which you are connected.
You have to add some_existing_db to the psql invocations where you grant privileges to db_reader.
In MySQL, I used use database_name;
What's the psql equivalent?
In PostgreSQL, you can use the \connect meta-command of the client tool psql:
\connect DBNAME
or in short:
\c DBNAME
You can connect to a database with \c <database> or \connect <database>.
At the PSQL prompt, you can do:
\connect (or \c) dbname
You can select the database when connecting with psql. This is handy when using it from a script:
sudo -u postgres psql -c "CREATE SCHEMA test AUTHORIZATION test;" test
use \c databaseName or \connect databaseName
(Working on psql 13.3)
\l for databases
\c DatabaseName to switch to db
\df for procedures stored in particular database
Though not explicitly stated in the question, the purpose is to connect to a specific schema/database.
Another option is to directly connect to the schema. Example:
sudo -u postgres psql -d my_database_name
Source from man psql:
-d dbname
--dbname=dbname
Specifies the name of the database to connect to. This is equivalent to specifying dbname as the first non-option argument on the command line.
If this parameter contains an = sign or starts with a valid URI prefix (postgresql:// or postgres://), it is treated as a conninfo string. See Section 31.1.1, “Connection Strings”, in the
documentation for more information.
Using psql's meta-command \c or \connect [ dbname [ username ] [ host ] [ port ] ] | conninfo (see documentation).
Example: \c MyDatabase
Note that the \c and \connect meta-commands are case-sensitive.
Use below statement to switch to different databases residing inside
your postgreSQL RDMS
\c databaseName
You can also connect to a database with a different ROLE as follows.
\connect DBNAME ROLENAME;
or
\c DBNAME ROLENAME;
You can connect using
\c dbname
If you would like to see all possible commands for POSTGRESQL or SQL follow this steps :
rails dbconsole
(You will be redirected to your current ENV database)
?
(For POSTGRESQL commands)
or
\h
(For SQL commands)
Press Q to Exit
If you want to switch to a specific database on startup, try
/Applications/Postgres.app/Contents/Versions/9.5/bin/psql vigneshdb;
By default, Postgres runs on the port 5432. If it runs on another, make sure to pass the port in the command line.
/Applications/Postgres.app/Contents/Versions/9.5/bin/psql -p2345 vigneshdb;
By a simple alias, we can make it handy.
Create an alias in your .bashrc or .bash_profile
function psql()
{
db=vigneshdb
if [ "$1" != ""]; then
db=$1
fi
/Applications/Postgres.app/Contents/Versions/9.5/bin/psql -p5432 $1
}
Run psql in command line, it will switch to default database; psql anotherdb, it will switch to the db with the name in argument, on startup.
Listing and Switching Databases in PostgreSQL
When you need to change between databases, you’ll use the \connect command, or \c followed by the database name as shown below:
postgres=# \connect database_name
postgres=# \c database_name
Check the database you are currently connected to.
SELECT current_database();
PostgreSQL List Databases
postgres=# \l
postgres=# \list
Connect to database:
Method 1 : enter to db : sudo -u postgres psql
Connect to db : \c dbname
Method 2 : directly connect to db : sudo -u postgres psql -d my_database_name
You can just enter use [dbName] to switch between databases without reentering your password.
So what I want to do here is to run a script while connected to a database I already had using pgAdmin3. The script contains a create role, tablespace, database and a create schema and several tables under that schema.
The problem here is that when I run the script it creates the new role, tablespace and database correctly. It also creates the schema and the tables correctly but with a problem, the schema is created under the database, from which I ran the script, instead of the newly created database. The script is more or less like this.
CREATE ROLE "new_role" ... ;
CREATE TABLESPACE "new_space"
OWNER "new_role"
LOCATION '/home/...';
CREATE DATABASE "new_db"
WITH OWNER = "new_role"
TABLESPACE = "new_space";
CREATE SCHEMA "schema" AUTHORIZATION "new_role" ;
CREATE TABLE IF NOT EXISTS "schema"."new_table"(
...
) TABLESPACE "new_space";...
...
I already saw a solution with a \connect foo; but that is not what I wanted, I wanted it to somehow connect within the script without running things separately and running \connect foo in the terminal.
Can anyone tell me if there is anyway to do this and help me come out with a solution to this problem?
Use psql and split it up into two scripts . You can save the scripts in .sql files, and then run psql to connect to the DB you want to run each script against all on the same command line (with && in between each command). The two psql commands could be combined into one bash script so it's only one command that you need to run.
Something like this, if the script were named foo.sql:
psql -X -h <host> -U <user> -p <port> -f foo.sql <db_name>
The first script could have the create role, create tablespace and create database commands, connecting to the postgres db or a template DB, and the second script could have the rest of the commands.
You could also use createdb from the bash script instead of CREATE DATABASE.
Using pgAdminIV:
1- right click on default database "postgres"
2- select create database, give a name f.e. "newdatabase"
3- click on "newdatabase" (to establish connection)
4- open the query tool
5- import, write or paste your code
6- run your code f.e.: CREATE SCHEMA newschema;
It works for me...
I'm searching for a simple way to delete all data from a database and keep the structure (table, relationship, etc...).
I using postgreSQL but I think, if there a command to do that, it's not specific to postgres.
Thanks,
Damien
Dump the schema using pg_dump. drop the database, recreate it and load the schema.
Dump you database schema (the -s tag) to a file:
pg_dump -s -f db.dump DB-NAME
Delete the database:
dropdb DB-NAME
Recreate it:
createdb DB-NAME
Restore the schema only:
pg_restore db.dump > psql DB-NAME
This should work on PostgreSQL; Other DBMS might have their own tools for that. I do no know of any generic tool to do it.
EDIT:
Following comments, you might want to skip the dropdb command, and simply create another database with the dumped schema. If all went through well, you can drop the old database:
pg_dump -s -f db.dump DB-NAME
createdb DB-NEW-NAME
pg_restore db.dump > psql DB-NEW-NAME
At this point, you have the full database at DB-NAME, and an empty schema at DB-NEW-NAME. after you're sure everything is OK, use dropdb DB-NAME.
You can do something like this:
export PGUSER=your_pg_user
export PGHOST=database.host
export PGPORT=port
export PGDATABASE=your_database
psql -qAtX -c "select 'TRUNCATE table ' || quote_ident(table_schema) || '.' || quote_ident(table_name) || ' CASCADE;' from information_schema.tables where table_type = 'BASE TABLE' and not table_schema ~ '^(information_schema|pg_.*)$'" | psql -qAtX
It will do what's necessary.
Of course these exports are not necessary, but they will make it simpler to run 2 copies of psql without having to givem them all standard -U, -d, and so on, switches.
One thing though - using TRUNCATE to do so, while faster than DELETE, has it's drowbacks - for example - it is not being replicated by Slony and any other replication system that works on triggers. Unless you are working on PostgreSQL 8.4, and your replication knows how to use triggers on TRUNCATE.
I'm not a Postgres guy, but one option would be to iterate through the tables and issue a Truncate command against each one. You'll have to take otable relationships into account, though - you will not be able to delete reference data before data that refers to it, for example.
In pgAdmin you can do:
Right-click database -> backup, select "Schema only"
Drop the database
Create a new database and name it like the former
Right-click the new database -> restore -> select the backup, select "Schema only"
your can delete all records of your database without restriction of foreign keys by following three steps
Take script of your Database
Right Click on your database (your DB Name)
click on task and then "Generate script"
Specify location
Delete your database base
recreate a database with the same name and run you generated script
This way you can empty all of your database