Question

我有一个查询来自多个数据库的SELECT，其中'auth'= mad：

$result = mysql_query("SELECT * FROM test.1 WHERE auth = 'mad' LIMIT 1 
    UNION SELECT * FROM test.2 WHERE auth = 'mad' LIMIT 1 
    UNION SELECT * FROM test.3 WHERE auth = 'mad' LIMIT 1");

如何标记或分类从test.1获得的结果; test.2或test.3？

非常感谢。

Answer 1

将表名添加到结果中：

$result = mysql_query("SELECT *, 'test.1' FROM test.1 WHERE auth = 'mad' LIMIT 1 
                  UNION SELECT *, 'test.2' FROM test.2 WHERE auth = 'mad' LIMIT 1 
                  UNION SELECT *, 'test.3' FROM test.3 WHERE auth = 'mad' LIMIT 1");

Answer 2

$result = mysql_query("SELECT *, 'test1' as Source FROM test.1 WHERE auth = 'mad' LIMIT 1 
UNION SELECT *, 'test2' FROM test.2 WHERE auth = 'mad' LIMIT 1 
UNION SELECT *, 'test3' FROM test.3 WHERE auth = 'mad' LIMIT 1");

Answer 3

如果我理解正确，您只需添加一列。此外，最好使用union all而不是union，因为union也会花费额外的精力来消除重复项：

SELECT 1 as test, t1.* FROM test.1 t1 WHERE auth = 'mad' LIMIT 1 
    UNION ALL
SELECT 2 as test, t2.* FROM test.2 t2 WHERE auth = 'mad' LIMIT 1 
    UNION ALL
SELECT 3 as test, t3.* FROM test.3 t3 WHERE auth = 'mad' LIMIT 1;

“分类”或“标记”SELECT查询

3 个答案: