Suppose the following tables in MySQL describe the documents contained in folders.
mysql> select * from folder;
+----+----------------+
| ID | PATH |
+----+----------------+
| 1 | matches/1 |
| 2 | matches/2 |
| 3 | shared/3 |
| 4 | no/match/4 |
| 5 | unreferenced/5 |
+----+----------------+
mysql> select * from DOC;
+----+------+------------+
| ID | F_ID | DATE |
+----+------+------------+
| 1 | 1 | 2000-01-01 |
| 2 | 2 | 2000-01-02 |
| 3 | 2 | 2000-01-03 |
| 4 | 3 | 2000-01-04 |
| 5 | 3 | 2000-01-05 |
| 6 | 3 | 2000-01-06 |
| 7 | 4 | 2000-01-07 |
| 8 | 4 | 2000-01-08 |
| 9 | 4 | 2000-01-09 |
| 10 | 4 | 2000-01-10 |
+----+------+------------+
The column identifiers are primary keys, and the F_ID column of the DOC table is a non-empty foreign key that refers to the primary key of the FOLDER table. Using the "DATE" of documents in the where clause, I would like to find which folders contain only the selected documents. For documents earlier than 2000-01-05, this can be written as:
SELECT DISTINCT d1.F_ID
FROM DOC d1
WHERE d1.DATE < '2000-01-05'
AND d1.F_ID NOT IN (
SELECT d2.F_ID
FROM DOC d2 WHERE NOT (d2.DATE < '2000-01-05')
);
'1' '2'.
http://dev.mysql.com/doc/refman/5.5/en/rewriting-subqueries.html
, . , NOT IN JOINS, , . , , ?