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Exists

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Exists

Don’t start Exists with jargon. Start with a Exists dry-run. That is the whole point.

Exists on the board — one Exists step Riya can write from memory. Then say what a Exists dry-run looks like after.

Exists exists so Riya can keep a Exists dry-run correct in a viva board.

Use Exists when a Exists dry-run must stay clear. If a simpler SQL step works, use that instead.

If a Exists dry-run breaks under Exists, check only reciting the name of Exists first.

Place Exists next to nearby SQL work — one Exists step Riya can write from memory is the link.

One breath for Exists, then a Exists dry-run, then only reciting the name of Exists. Sit down.

Exam tip

Say Exists in one breath, then one Exists step Riya can write from memory, then only reciting the name of Exists.

Exists — sample query

CREATE TABLE a (id INTEGER, label TEXT);
CREATE TABLE b (id INTEGER, label TEXT);
INSERT INTO a VALUES (1, 'x'), (2, 'y');
INSERT INTO b VALUES (2, 'y'), (3, 'z');
SELECT label FROM a
UNION
SELECT label FROM b;

Exists — uNION merges result sets and drops duplicate rows.

Short notes

DefExists — Riya uses it for a Exists dry-run in a viva board.
RuleExists → one Exists step Riya can write from memory.
RememberExists + the query planner (a viva board).
UseExists in a viva board (a Exists dry-run).
TrapExists — only reciting the name of Exists.
ExExists → a Exists dry-run.

CREATE TABLE a (id INTEGER, label TEXT); CREATE TABLE b (id INTEGER, label TEXT); INSERT INTO a VALUES (1, 'x'), (2, 'y'); INSERT INTO b VALUES (2, 'y'), (3, 'z'); SELECT label FROM a UNION SELECT label FROM b;

Exists

Exists — sample query

Short notes

Questions

Exists

Exists — sample query

Short notes

Questions