當我遇到一些有趣的事情時,我試圖測量TINYINT和INT之間的差異。對於具有少量列的表,數據類型的選擇似乎不會影響表的大小。這些表爲什麼是相同的大小?
服務器版本:5.1.41-3ubuntu12.10(Ubuntu的)
實施例:
mysql> describe tinyint_test;
+----------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| test_int | tinyint(4) | YES | | NULL | |
+----------+------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> describe tinyint_id_test;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| id | tinyint(4) | YES | | NULL | |
+-------+------------+------+-----+---------+-------+
1 row in set (0.00 sec)
mysql> describe int_test;
+--------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------+------+-----+---------+-------+
| not_id | int(11) | YES | | NULL | |
+--------+---------+------+-----+---------+-------+
1 row in set (0.00 sec)
mysql> select * from tinyint_test;
+------+----------+
| id | test_int |
+------+----------+
| 1 | 1 |
| 2 | 2 |
| 3 | 127 |
| 10 | 50 |
+------+----------+
4 rows in set (0.00 sec)
mysql> select * from tinyint_id_test;
+------+
| id |
+------+
| 1 |
| 2 |
| 127 |
| 50 |
+------+
4 rows in set (0.00 sec)
mysql> select * from int_test;
+--------+
| not_id |
+--------+
| 1 |
| 2 |
| 127 |
| 50 |
+--------+
4 rows in set (0.00 sec)
mysql> SELECT TABLE_NAME, DATA_LENGTH FROM INFORMATION_SCHEMA.TABLES where TABLE_SCHEMA like '%test%';
+-----------------+-------------+
| TABLE_NAME | DATA_LENGTH |
+-----------------+-------------+
| int_test | 28 |
| tinyint_id_test | 28 |
| tinyint_test | 28 |
+-----------------+-------------+
3 rows in set (0.00 sec)
我隱約懷疑有可能是在每行中的內部列,或者該最小數據大小對於一個給定的行必須至少是一個完整的INT的大小,但這些懷疑都不能解釋這裏發生的事情。什麼可能是這樣的情況是我選擇DATA_LENGTH是測量表的真實大小的不正確的工具,在這種情況下,一個可接受的答案會指向我實際測量這些表的正確方向。
編輯:
我可以用兩個整數生成不同大小的表:
mysql> describe int_id_test;
+----------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| test_int | int(11) | YES | | NULL | |
+----------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)
mysql> select * from int_id_test;
+------+----------+
| id | test_int |
+------+----------+
| 1 | 1 |
| 2 | 2 |
| 3 | 127 |
| 10 | 50 |
+------+----------+
4 rows in set (0.00 sec)
mysql> SELECT TABLE_NAME, DATA_LENGTH FROM INFORMATION_SCHEMA.TABLES where TABLE_SCHEMA like '%test%';
+-----------------+-------------+
| TABLE_NAME | DATA_LENGTH |
+-----------------+-------------+
| int_id_test | 36 |
| int_test | 28 |
| tinyint_id_test | 28 |
| tinyint_test | 28 |
+-----------------+-------------+
4 rows in set (0.01 sec)
由於我的數據文件只是13 Gig的害羞,我不認爲這會工作。當我定義列時,括號中的大小號由我選擇的tinyint/int設置。我不相信這與問題有關。 – 2011-04-27 15:37:01