Differences from psql

-c, -f, -t, -A and -x mean what they mean in psql, so this prints a bare number in either program:

$ hsql -tAc "select count(*) from orders"

It prints it the same way against every adapter, which is the part psql cannot do.

What Is Different

	psql	hsql
`-P`	`--pset`, an output setting	`--profile`, a config-file profile
Field separator	`-F`	`--csv`, `--format tsv`, or any other `--format`
Listing databases	`-l`	`--catalog`
Describing an object	`\d`, `\dt`	`--catalog --path`, `--catalog-search`
Stopping on the first error	`-v ON_ERROR_STOP=1`	`--on-error stop`, the default
One transaction	`-1`	write `begin` and `commit` in your script
`-o`	a file for query output	a file, or a directory that gets one file per result set
Connection flags	`-h`, `-p`, `-U`, built in	the adapter’s, so `hsql --help -a postgres` lists them
Row limits	none	500 rows by default; `--limit -1` removes it
Suppressing chatter	`-q`	nothing to suppress: stdout is only ever results
Exit codes	`1` its own error, `2` connection, `3` script error	`1` query error, `2` usage/config, `3` connection, `4` timeout

Warning

-t is tuples only, as in psql, not Harlequin’s theme flag. Connection strings are positional, so hsql -t nord -c "..." parses, nord becomes a connection string, and hsql says so on stderr.

No Backslash Commands

hsql has no meta-commands. What they do, options do:

\d, \dt, \l — --catalog and --catalog-search, which produce ordinary result sets.
\copy — --csv and -o, or --format parquet.
\timing — --stats, which reports elapsed_ms on stderr.
\c — a different profile: -P NAME.
\set — the profile, or the command line. One invocation, no session variables.

Sessions: Keeping Connections Open

By default, hsql executes what it was passed and exits. Every invocation starts a process, connects, runs its SQL and drops the connection, so nothing it did — a temp table, a SET, an open transaction — reaches the next one. That is the right default for a script or an agent, and it is what every example above assumes.

hsql --serve prod -P prod holds a connection open the way a psql prompt does, and hsql --session prod -c "..." runs against it. There is still no interactive prompt — for that, Harlequin uses the same adapters, config files and profiles: harlequin -P prod — but an invocation served that way answers in milliseconds instead of reconnecting, and finds the temp tables, settings and transactions the one before it left, exactly as a psql session would. See Warm Sessions.