Question

Some interactive shells have a built-in variable that always points to the results of the previous command (for example in the python3 shell this variable is “_”).

Does any such variable exist in the Sqlite3 and Psql prompts?

Answer 1

psql doesn’t, and it’s not really a typical way to work with relational data. If you want to retain the result from a previous query, put it in a temporary table.

Do you mean that you want to be able to:

SELECT count(somecol), avg(someothercol) FROM _;

… for example? ie you want to be able to use your “last result” set and perform further processing on it?

If so, it’s usually best to:

• Put the results into a temporary table using SELECT INTO. This works for pretty much anything, including ordinary SELECT, DELETE ... RETURNING, INSERT ... RETURNING, UPDATE ... RETURNING, etc. Then process the temporary table as desired.
• Create a temporary view of the result. This will of course only work for SELECT. CREATE TEMPORARY VIEW makes a view that only exists for your session.
• Use readline. Just press the up arrow to get to your previous command, edit as desired, re-run.
• Use the \e psql command to open the last command in an external editor (specified with the env var EDITOR) where you can modify it more easily.

SQLite won’t have a \e command and I don’t think it has DML commands that can return result sets (... RETURNING commands). Otherwise most of that should apply there too.