如何將一個表中的行值用作一個查詢中另一個表的名稱？

Question

我甚至不知道我的頭銜是否有意義，所以希望我的解釋能夠彌補我的標題清晰度。

我想創建一個返回關於我的表的一般信息，行數，平均長度，數據長度單個查詢，分（ID）和max（ID）值等

我知道如何查詢INFORMATION_SCHEMA.PARTITIONS以獲取「大小」信息。例如：

mysql> SELECT TABLE_NAME AS Name, 
    ->  TABLE_ROWS as 'Row Count', 
    ->  AVG_ROW_LENGTH AS 'Avg Row Len', 
    ->  DATA_LENGTH, 
    ->  ROUND(DATA_LENGTH/1024/1024) AS 'DATA_LENGTH(M)' 
    -> 
    -> FROM INFORMATION_SCHEMA.PARTITIONS 
    -> 
    -> WHERE (TABLE_NAME = 'event_log' 
    ->  OR TABLE_NAME = 'event_log_policy_entries' 
    ->  OR TABLE_NAME = 'event_log_policy_status'); 
+--------------------------+-----------+-------------+-------------+----------------+ 
| Name      | Row Count | Avg Row Len | DATA_LENGTH | DATA_LENGTH(M) | 
+--------------------------+-----------+-------------+-------------+----------------+ 
| event_log    | 10000089 |   182 | 1822425088 |   1738 | 
| event_log_policy_entries | 10000137 |   171 | 1710227456 |   1631 | 
| event_log_policy_status | 10000094 |   244 | 2449473536 |   2336 | 
+--------------------------+-----------+-------------+-------------+----------------+ 
3 rows in set (0.57 sec) 

mysql> 

而且，我知道如何使用在每個表的基礎上MIN()和MAX()函數來獲得他們的最小/最大ID值。 （我所有的三個表都有一個名爲id的列）。

mysql> SELECT MIN(id) AS 'Min', MAX(id) AS 'Max' from event_log; 
+------+---------+ 
| Min | Max  | 
+------+---------+ 
| 0 | 9999999 | 
+------+---------+ 
1 row in set (0.00 sec) 

mysql> 

但是我不知道如何使這個一個查詢。我的目標是將有一個表，如下所示：

+--------------------------+-----------+-------------+-------------+----------------+-----+-----+ 
| Name      | Row Count | Avg Row Len | DATA_LENGTH | DATA_LENGTH(M) | Min | Max | 
+--------------------------+-----------+-------------+-------------+----------------+-----+-----+ 
| event_log    | 10000089 |   182 | 1822425088 |   1738 | # | # | 
| event_log_policy_entries | 10000137 |   171 | 1710227456 |   1631 | # | # | 
| event_log_policy_status | 10000094 |   244 | 2449473536 |   2336 | # | # | 
+--------------------------+-----------+-------------+-------------+----------------+-----+-----+ 

我一直在閱讀有關表連接和子查詢，但我一直沒能想出解決辦法，但。 （我假設這可以通過一個查詢完成）。

Answer 1

一位同事誰不是一個堆棧溢出用戶提到我作爲一個例子，我則推斷爲以下：

mysql> SELECT TABLE_NAME AS Name, 
    ->  AVG_ROW_LENGTH AS 'Avg_Row_Size', 
    ->  DATA_LENGTH AS 'Table_Size', 
    ->  INDEX_LENGTH AS 'Index_Size', 
    ->  elog.Min, 
    ->  elog.Max 
    -> 
    -> FROM INFORMATION_SCHEMA.PARTITIONS AS isp 
    -> 
    -> LEFT JOIN 
    -> (SELECT 'event_log' AS 'Name', 
    ->   MIN(id) AS 'Min', 
    ->   MAX(id) AS 'Max' 
    -> FROM event_log 
    -> UNION 
    -> (SELECT 'event_log_policy_entries' AS 'Name', 
    ->   MIN(id) AS 'Min', 
    ->   MAX(id) AS 'Max' 
    ->  FROM event_log_policy_entries) 
    ->  UNION 
    ->  (SELECT 'event_log_policy_status' AS 'Name', 
    ->    MIN(id) AS 'Min', 
    ->    MAX(id) AS 'Max' 
    ->  FROM event_log_policy_status)) AS elog ON (elog.Name = isp.TABLE_NAME) 
    -> 
    -> WHERE (isp.TABLE_NAME = 'event_log' 
    ->  OR isp.TABLE_NAME = 'event_log_policy_entries' 
    ->  OR isp.TABLE_NAME = 'event_log_policy_status'); 
+--------------------------+--------------+------------+------------+------+---------+ 
| Name      | Avg_Row_Size | Table_Size | Index_Size | Min | Max  | 
+--------------------------+--------------+------------+------------+------+---------+ 
| event_log    |   182 | 1822425088 |   0 | 11 | 9999999 | 
| event_log_policy_entries |   170 | 1709178880 | 137019392 | 33 | 9999999 | 
| event_log_policy_status |   244 | 2448392192 | 137019392 | 132 | 9999999 | 
+--------------------------+--------------+------------+------------+------+---------+ 
3 rows in set (0.56 sec) 

mysql> 

這似乎是一樣快，因爲這並沒有原始查詢有最小值/最大值。我使用了SELECT和UNION來創建一個帶有名稱和最小/最大值的子表，然後將它加入到INFORMATION_SCHEMA.PARTITION TABLE_NAME的結果中。

有沒有更好的方法來做到這一點？這是有效的，我覺得搞清楚這一點很好。但是有更好的方法嗎？

Answer 2

試試這個：

mysql> SELECT TABLE_NAME AS Name, 
    ->  TABLE_ROWS as 'Row Count', 
    ->  AVG_ROW_LENGTH AS 'Avg Row Len', 
    ->  DATA_LENGTH, 
    ->  ROUND(DATA_LENGTH/1024/1024) AS 'DATA_LENGTH(M)', 
    ->  MIN(id) AS 'Min', MAX(id) AS 'Max' 
    -> 
    -> FROM INFORMATION_SCHEMA.PARTITIONS, event_log 
    -> 
    -> WHERE (TABLE_NAME = 'event_log' 
    ->  OR TABLE_NAME = 'event_log_policy_entries' 
    ->  OR TABLE_NAME = 'event_log_policy_status'); 

它將從INFORMATION_SCHEMA.PARTITIONS返回過濾的結果，所有從EVENT_LOG結果。

我有一個問題，是否有event_log表中的一個字段可以與INFORMATION_SCHEMA.PARTITIONS表相關聯，以便您可以將event_log的每一行綁定到INFORMATION_SCHEMA.PARTITIONS表中的一行？