mysql - 如何使用选择查询查找表名

Question

SELECT product FROM Table_name_1 
WHERE id = '% textbox1.text %'  
UNION  
SELECT product FROM Table_name_2 
WHERE id = '% textbox1.text %'  
UNION  
SELECT product FROM Table_name_3
WHERE id = '% textbox1.text %' 

通过这个代码，我能够获取产品。但我怎么知道这个结果是从哪个表中取出的呢？所以我也想知道表名。

Answer 1

您还可以选择常量值并为其指定列名称。

SELECT product, 'Table_name_1' as table FROM Table_name_1 WHERE id = '% textbox1.text %'
UNION
SELECT product, 'Table_name_2' as table FROM Table_name_2 WHERE id = '% textbox1.text %' 
UNION
SELECT product, 'Table_name_3' as table FROM Table_name_3 WHERE id = '% textbox1.text %'