示例：SQLFiddle

Question

我有这个查询。当我执行时，我得到了Query语句，但我想要这个查询的结果集。

我的查询是：

SELECT CONCAT('select * from ', table_name, ' union all ') AS CUSTOMQUERY
FROM   information_schema.tables
WHERE  table_name LIKE '%custom%'

我得到了这个结果

select * from custom_70006 union all  
select * from custom_704306 union all  
select * from custom_700436 union all  
select * from custom_7000643 union all  
select * from custom_7000634 union all  
select * from custom_700046 union all  
select * from custom_700063 union all  
select * from custom_700062 union all

但我希望此特定列的结果集包含相应的数据，并且最后union all应该删除。

请帮我查询相关问题。

Answer 1

我认为这就是你要找的东西：

SET GLOBAL group_concat_max_len = 4294967295;

SELECT @query1 := GROUP_CONCAT(CONCAT('SELECT * FROM ', table_name) SEPARATOR
                         ' UNION ALL ') AS CUSTOMQUERY
FROM   INFORMATION_SCHEMA.tables
WHERE  TABLE_SCHEMA = SCHEMA()
       AND table_name LIKE '%custom%';


PREPARE stmt FROM @query1; EXECUTE stmt; DEALLOCATE PREPARE stmt;

示例：SQLFiddle

或将您的查询修改为：

SELECT @query1 := CONCAT('select * from ', table_name, ' union all ') AS
       CUSTOMQUERY
FROM   information_schema.tables
WHERE  table_name LIKE '%custom%'

从查询中删除最后一个'union all'字符串：

SET @query1 = TRIM(TRAILING 'union all' FROM TRIM(@query1));

PS：group_concat_max_len的默认值仅为1024.因此您需要将其设置为更高的值，否则查询的输出将被剥离，您可能会遇到语法错误。

特定查询的结果集

1 个答案:

示例：SQLFiddle