如果第一个中没有足够的行，如何从另一个表中选择行？ 用SQL

Question

我有两张桌子：

表“项目”：

| id | name       | description                              |
| 1  | Michael    | This is a random description blabalbla   | 
| 2  | Tom        | This is another descriptions blablabla   | 

表“moreitems”：

| id | name       | description                              |
| 1  | Michael    | This is a random description blabalbla   | 
| 2  | Mike       | This is another descriptions blablabla   | 
| 3  | Michael    | This is a random description blabalbla   | 
| 4  | Blain      | This is another descriptions blablabla   | 

目前，我正在从第一个表中获取项目，如下所示：

SELECT * FROM items WHERE name = 'Michael' AND CHAR_LENGTH(description) > 10 LIMIT 3

如果尚未达到limit（3），我想在查询中包含第二个表。 我怎么能这样做 - 没有PHP？

Answer 1

尝试：

SELECT * FROM
(SELECT 'items' table_name, i.* 
 FROM items i WHERE name = 'Michael' AND CHAR_LENGTH(description) > 10 
 UNION ALL 
 SELECT 'moreitems' table_name, m.* 
 FROM moreitems m WHERE name = 'Michael' AND CHAR_LENGTH(description) > 10 
 ORDER BY 1,2) v
LIMIT 3