psql can be a little bit intimidating in the begining, following this doc should help you get more familiar.
\q
\du
-- for listing databases
\l
-- for listing databases with additional info including size
\l+
You can also list databases which match a pattern. For example, the below command will list add databases which have abc as part of their name.
\l *abc*
\c[onnect] {[DBNAME|- USER|- HOST|- PORT|-] | conninfo}
You can use this to connect to another postgresql host or even another database on that host. For example, the command below will connect to pg_bench database on the same host.
\c pg_bench
-- for listing tables
\dt
-- for listing tables with additional info including size
\dt+
Similar to databases, pattern search works here as well.
\dt+ *abc*
Sometimes, the output of query doesn't fit the window and its hard to read/understand the result. Expanded output helps in these cases.
\x
If you want to make this switch between expanded view automatically, use this.
\x auto
A lot of times, while debugging an issue, you need to know the schema of a table or a view.
\d {name}
-- execute commands from a file
\i {file_path}
-- send query's outputs to file
\o {file_path}
-- to revert back to stdout
\o
-- edit last query in buffer
\e
-- show last query in buffer
\p
-- save last query in buffer to file
\w file_path
-- show query history
\s
-- to save history to file
\s {file_path}
-- execute last query periodically (default: 2s)
\watch {period_in_seconds}
-- query execution time
\timing
You can place a .psqlrc file at ~/.psqlrc to customize psql.
\set QUIET 1
-- print null as "[null]" in output. Its useful while debugging since empty string & null show up as same in output
\pset null '[null]'
-- autocomplete words are in upper case
\set COMP_KEYWORD_CASE upper
-- print time taken by query for execution
\timing on
\set HISTSIZE 2000
-- switch to expanded output depending on output length
\x auto
\set VERBOSITY verbose
\set HISTCONTROL ignoredups
\set QUIET 0
More details here: https://wiki.postgresql.org/wiki/Psqlrc
\h SELECT
It is a little hard to remember all the slash commands when starting out. Use \? to get a list of all slash commands in psql even the ones not covered above.