如何编写子查询以动态地从未确定的表中获取相同的字段

Posted 2023-05-08

【中文标题】如何编写子查询以动态地从未确定的表中获取相同的字段

【英文标题】：How to write subquery to get the same fields from undetermined tables dynamically

【发布时间】：2021-12-29 04:42:59

【问题描述】：

SELECT SUM(t.orgBilledDuration/60) AS Duration
FROM 
(SELECT orgBilledDuration FROM Successfuliptsp.vbSuccessfulCDR_631
     WHERE FROM_UNIXTIME(connectTime/1000, '%Y-%m-%d %H:%i:%s') BETWEEN '2021-10-20 00:00:00' AND '2021-12-05 23:59:59'
 UNION ALL
 SELECT orgBilledDuration FROM Successfuliptsp.vbSuccessfulCDR_632
     WHERE FROM_UNIXTIME(connectTime/1000, '%Y-%m-%d %H:%i:%s') BETWEEN '2021-10-20 00:00:00' AND '2021-12-05 23:59:59'
 UNION ALL
 SELECT orgBilledDuration FROM Successfuliptsp.vbSuccessfulCDR_633
     WHERE FROM_UNIXTIME(connectTime/1000, '%Y-%m-%d %H:%i:%s') BETWEEN '2021-10-20 00:00:00' AND '2021-12-05 23:59:59'
) t

从上面的 SQL 中，我尝试编写以下查询来动态地从未确定的表中选择相同的字段。以下查询动态给出一张表的结果，但需要动态编写上述子查询。有人可以就此提出建议吗？

每个嵌套的 select 语句都适用于按月计算的表。需要从不同月份的表中搜索

SET @tab_id:= 631;
SET @tab:= concat('Successfuliptsp.vbSuccessfulCDR_',@tab_id);
SET @ID_1:= 'FROM_UNIXTIME(connectTime/1000, ''%Y-%m-%d %H:%i:%s'') BETWEEN ''2021-11-25 00:00:00'' AND ''2021-11-30 23:59:59''';
SET @s = CONCAT('select SUM(orgBilledDuration)/60 from ', @tab, ' where ', @ID_1); 
PREPARE STMT1 FROM @s; 
EXECUTE STMT1; 
DEALLOCATE PREPARE STMT1;

【参考方案1】：

SET @s1:='SELECT SUM(t.orgBilledDuration/60) AS Duration FROM (';
SET @s2:='SELECT orgBilledDuration FROM Successfuliptsp.vbSuccessfulCDR_';
SET @s3:=' WHERE FROM_UNIXTIME(connectTime/1000, ''%Y-%m-%d'') BETWEEN ''2021-10-20'' AND ''2021-12-05''';
SET @s4:=') t';

SELECT CONCAT(@s1,
              GROUP_CONCAT(CONCAT(@s2,
                                  numbers.tab_no,
                                  @s3)
                           SEPARATOR ' UNION ALL '),
              @s4)
INTO @s
FROM ( SELECT 631 tab_no UNION ALL
       SELECT 632 UNION ALL
       SELECT 633 ) numbers;

PREPARE stmt FROM @s; 
EXECUTE stmt; 
DROP PREPARE stmt;

https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=ee5e3a98a43d70443135ce76bee56d74