One-Shot Query vs Interactive REPL: DB CLIs Fork on One Flag

After connecting, DB CLIs fork on one thing: pass a query flag for a one-shot run, omit it to drop into a REPL. Plus the psql/mysql/mongosh flags and clean-output options.

After connecting (same five coordinates), the only fork is whether you pass a query flag:

Pass a query flag and it runs once. Omit it and you drop into a REPL.

	One-shot (stay in shell)	Interactive (REPL)
psql	`-c "…"` / `-f file`	`psql <uri>` → `dbname=#`, quit `\q`
mysql	`-e "…"` / `< file`	`mysql <flags>` → `mysql>`, quit `exit`
mongosh	`--eval "…"` / `--file`	`mongosh <uri>` → `>`, quit Ctrl-D

The language inside the REPL differs: psql / mysql are SQL (mysql needs a trailing ;, psql’s \ meta-commands take no ;). Mongosh is a JavaScript REPL wired to db. For scripting, add clean-output flags: psql -tA, mysql -BN, mongosh --quiet.

From this session: psql … -c "\dt" ran a backslash meta-command one-shot (no ;) and returned to the shell. \dt only lists the search-path schema (public), while \dt *.* lists all schemas.

The only fork after connecting is the query flag: with one it is one-shot, without one it is a REPL.

References

psql documentation: https://www.postgresql.org/docs/current/app-psql.html

Related: back to the remote DB overview. This runs on the five coordinates, and the MySQL side is four ways to feed inline SQL.

Tags #databases #cli