mysql - 执行 UNION select 获取数据来自哪个表

Question

我有 3 个表共享完全相同的结构，例如：

id       name_col

我有这个查询：

$query = mysql_query("SELECT * FROM tbl_1 UNION SELECT * FROM tbl_2 UNION SELECT * FROM tbl_3");

现在：

while($row = mysql_fetch_array($query)){
    names .= $row['name_col'];
    // HERE HOW I COULD KNOW WHICH TABLE THIS DATA IS COMING FROM?
    // THIS NAME IS FROM tbl_1 OR tbl_2 OR tbl_3
}

Answer 1

您还可以添加一个自定义列，指定它所属的表的名称，例如

SELECT id, name_col, 'table1' tableName FROM table1
UNION
SELECT id, name_col, 'table2' tableName FROM table2
UNION
SELECT id, name_col, 'table3' tableName FROM table3

Answer 2

您可以将常量字段添加到子查询中以对其进行索引，如下所示：

SQL：

SELECT *, 1 AS tbl ROM tbl_1 
UNION
SELECT *, 2 AS tbl FROM tbl_2 
UNION
SELECT *, 3 AS tbl FROM tbl_3

该额外字段的列名必须在子查询中保持一致。

PHP：

while($row = mysql_fetch_array($query)){
    names .= $row['name_col'];
    switch ($row['tbl']){
         case 1: // tbl_1
         break;
         // etc.
    }
}