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joplin notion extension/Web Development/sql/postgresql.md
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joplin notion extension/Web Development/sql/postgresql.md
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postgresql
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- Installation
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https://www.geeksforgeeks.org/how-to-install-postgresql-on-arch-based-linux-distributions-manjaro/
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https://gist.github.com/NickMcSweeney/3444ce99209ee9bd9393ae6ab48599d8
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- To use it
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`sudo su - postgres`
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or
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`psql -U postgres`
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Creating database when in user
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`create database <database_name>`
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delete database
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`drop database <database_name>`
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- Remote connection
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`psql -U postgres -p 5432 -h hostname` (5432 is default postgresql port number)
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or
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`psql -U postgres -p 5432 -h hostname -d database_name`
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-U is username
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-p for port
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-h for hostname
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-d for database name
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To directly connect with url
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`psql postgres://user:password@ip_add_or_domain:port/db_name`
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or
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`PGPASSWORD="your_password" psql -U your_username -d your_database -h your_host`
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- Import and export
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Exporting postgresql Database
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We need to create a dump file. Here smart-brain is name of database
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`pg_dump -U postgres smart-brain > dump.sql`
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for remote
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`pg_dump -U postgres -p 5432 -h hostname -d database_name > dump.sql`
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Importing postgresql Database
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`psql -U postgres smart-brain < dump.sql`
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for archive compressed backups and restore
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backup
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` pg_dump -U synapse_user -p 5432 -h localhost -d -Fc synapse > synapse_backup1.dump`
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restore
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`pg_restore -U synapse_user -p 5432 -h localhost -d synapse1 synapse_backup1.dump`
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- Store query output in a file
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`psql -d DatabaseName -U UserName -c "SELECT * FROM TABLE" -o /root/Desktop/file.txt`
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Saving query output in csv file
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https://stackoverflow.com/questions/1517635/save-pl-pgsql-output-from-postgresql-to-a-csv-file
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By using a meta command `\copy`
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`\copy (Select * From foo) To '/tmp/test.csv' With CSV DELIMITER ',' HEADER`
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- Sometimes there is a error `current transaction is aborted, commands ignored until end of transaction block` then run this query
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`commit;` to fix this
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insert only if the record with paricular value dont exist
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here unique_column is column with must have unique constraint. it must be a key
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```sql
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INSERT INTO table_name (column1, column2)
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VALUES (val1, val2)
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ON CONFLICT (unique_column) DO NOTHING;
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```
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- set password of postgres user
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`ALTER USER username WITH PASSWORD 'newpassword';`
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# Setup Postgresql
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> run postgresql with systemctl
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### Install postgres
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##### latest
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`sudo pacman -S postgresql`
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##### specific version
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> find version & build from source
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### Check version
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`postgres --version`
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### Confirm psql is not running
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`sudo systemctl status postgresql` --> should not be running
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### Login as the postgres user
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> Note: always do this any time you are doing any type of admin work on psql
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`sudo su - postgres`
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### Initialize data directory
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> Note: default db for psql is /var/lib/postgres/data
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`initdb --locale en_US.UTF-8 -D /var/lib/postgres/data`
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### Logout of **postgres** user
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`exit`
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### Confirm psql is still not running
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`sudo systemctl status postgresql` --> should not be running
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### Start psql
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`sudo systemctl start postgresql`
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### Confirm psql is running
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`sudo systemctl status postgresql` --> should be active
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## Create user
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### Log into postgres
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`sudo su - postgres`
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### Create a new user
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> Note: user can be called anything however if you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).
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`createuser --interactive`
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or
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`sudo -u postgres bash`
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`createuser --pwprompt synapse_user`
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and for db
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`createdb --encoding=UTF8 --locale=C --template=template0 --owner=synapse_user synapse`
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- Enter name of role to add: `MY_LINUX_USERNAME` (add youur linux user else psql command wont work when using with that user )
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- Shall the new role be a superuser?: `y`
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### Logout of **postgres** user
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`exit`
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### Restart psql
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`sudo systemctl restart postgresql`
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### Confirm psql is running
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> Note: can see that it was restarted by looking at the timestamp on the ***Active*** field
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`sudo systemctl status postgresql`
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### Managing users
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To login as a newly created user in PostgreSQL, you typically need to use a client or interface that supports PostgreSQL, such as `psql`, PgAdmin, or another tool that allows database interaction. Here's how you can do it using `psql`, the command-line tool for PostgreSQL.
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1. **Create the User**: First, you need to create the user (if you haven't done so already). You can do this by connecting to your PostgreSQL instance as a superuser (often `postgres`) and running a command like the following:
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First type
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`psql -U postgres`
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```sql
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CREATE USER my_new_user WITH PASSWORD 'password';
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```
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Adjust `my_new_user` and `'password'` according to your preferences.
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2. **Grant Permissions** (if needed): Depending on what you want this user to do, you'll likely need to grant them some permissions or access to a database. Here's an example of how you can grant all privileges on a database named `my_database` to your new user:
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```sql
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GRANT ALL PRIVILEGES ON DATABASE my_database TO my_new_user;
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```
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3. **Login Using `psql`**: To login as the new user from the command line using `psql`, you would use a command like this:
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```bash
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psql -d my_database -U my_new_user -W
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```
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- `-d my_database` specifies the database you are connecting to.
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- `-U my_new_user` specifies the user you are logging in as.
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- `-W` prompts `psql` to ask for the password of the user. (Note: For security reasons, it's recommended to use `-W` to prompt for the password instead of passing it directly in the command line.)
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4. **Enter the Password**: After executing the above command, you'll be prompted to enter the password for `my_new_user`. Enter the password you have set for this account, and you should be logged in.
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5. **Using Other Tools**: If you are using a GUI-based tool like PgAdmin, the process involves:
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- Open PgAdmin and connect to your PostgreSQL server.
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- Create a new server connection if your user has access to a different server or database.
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- To delete users
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`drop user <username>`
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- Adding password for local connections
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By default there is `trust` authentication flag in `pg_hba.conf` file so we can login without requiring password. To change that just change trust to md5
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Location of `pg_hba.conf` : `/var/lib/postgres/data/pg_hba.conf`
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Other authenticaor flags are
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- trust allows the connection without a password.
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- peer uses the operating system user identity to authenticate (common for local connections).
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- md5 or scram-sha-256 require a password
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- Changing password
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`alter user tpost with password 'qwerty';`
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- Schema public permission error
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When creating table u may get error like
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`ERROR: permission denied for schema public`
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Then login to superuser ie `postgres`
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then run this
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`GRANT USAGE ON SCHEMA public TO tpost;`
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to grant permission
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Then restart the postgresql service
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- running sql script in postgresql
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`psql -U username -d database_name`
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then
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`\i /path/to/your/script.sql;`
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Alternatively, you can execute the script directly from the command line without entering the MySQL shell
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`psql -U username -d database_name -f /path/to/your/script.sql`
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in debian
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https://neon.tech/postgresql/postgresql-getting-started/install-postgresql-linux#connect-to-the-postgresql-database-server
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use this to login to psql
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`sudo -u postgres psql`
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or
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```sh
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sudo -i -u postgres
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# then
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psql
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```
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or
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`psql -U postgres -p 5432 -h localhost`
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for non interactive password use
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`PGPASSWORD=PASS psql -U postgres -p 5432 -h localhost` or `psql postgresql://postgres:PASS@localhost:5432`
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check database
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Many ways. Du -sh the folder. Dbdump the database, and there's a psql command for all the statistics too
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SELECT pg_size_pretty(pg_total_relation_size('"<schema>"."
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or
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for specific database
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`SELECT pg_size_pretty(pg_database_size('your_database_name'));`
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shortcut
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`\l+ your_database_name`
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for all database
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```sql
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SELECT datname AS database_name,
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pg_size_pretty(pg_database_size(datname)) AS size
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FROM pg_database
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ORDER BY pg_database_size(datname) DESC;
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```
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shortcut
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`\l+`
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https://stackoverflow.com/questions/2596624/how-do-you-find-the-disk-size-of-a-postgres-postgresql-table-and-its-indexes
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