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CREATE TABLE t1 (id INT) SELECT 1 id UNION SELECT 2 UNION SELECT 3;
CREATE TABLE t2 (id INT) SELECT 1 id UNION SELECT 2;
SELECT *
FROM t1
LEFT JOIN t2 ON t1.id = t2.id;
| id | id |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | null |
SELECT *
FROM t1
LEFT JOIN t2 ON t1.id = t2.id
WHERE t1.id = 1;
| id | id |
|---|---|
| 1 | 1 |
SELECT *
FROM t1
LEFT JOIN t2 ON t1.id = t2.id AND t1.id = 1;
| id | id |
|---|---|
| 1 | 1 |
| 2 | null |
| 3 | null |