如何将一个表中的行值用作一个查询中另一个表的名称？

Question

我甚至不知道我的头衔是否有意义，所以希望我的解释能够弥补我的标题清晰度。

我想创建一个返回关于我的表的一般信息，行数，平均长度，数据长度单个查询，分（ID）和max（ID）值等

我知道如何查询INFORMATION_SCHEMA.PARTITIONS以获取“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个表的基础上MIN()和MAX()函数来获得他们的最小/最大ID值。 （我所有的三个表都有一个名为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这个一个查询。我的目标是将有一个表，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 | # | # | 
+--------------------------+-----------+-------------+-------------+----------------+-----+-----+ 

我一直在阅读有关表连接和子查询，但我一直没能想出解决办法，但。 （我假设这可以通过一个查询完成）。

Answer 1

一位同事谁不是一个堆栈溢出用户提到我作为一个例子，我则推断为以下：

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> 

这似乎是一样快，因为这并没有原始查询有最小值/最大值。我使用了SELECT和UNION来创建一个带有名称和最小/最大值的子表，然后将它加入到INFORMATION_SCHEMA.PARTITION TABLE_NAME的结果中。

有没有更好的方法来做到这一点？这是有效的，我觉得搞清楚这一点很好。但是有更好的方法吗？

Answer 2

试试这个：

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'); 

它将从INFORMATION_SCHEMA.PARTITIONS返回过滤的结果，所有从EVENT_LOG结果。

我有一个问题，是否有event_log表中的一个字段可以与INFORMATION_SCHEMA.PARTITIONS表相关联，以便您可以将event_log的每一行绑定到INFORMATION_SCHEMA.PARTITIONS表中的一行？