在關係兩條表的mysql

Question

+--------------------------------------------+ 
|    category_table     | 
+----+--------------------+------------------+ 
+----+--------------------+------------------+ 
| id | cat_title   | parent   | 
+----+--------------------+------------------+ 
| 1 | cat1    | 0    | 
| 2 | cat2    | 1    | 
| 3 | cat3    | 1    | 
| 4 | cat4    | 2    | 
| 5 | cat5    | 2    | 
| 6 | cat6    | 2    | 
+----+--------------------+------------------+ 


+---------------------------------------------------------------+ 
|      content_table       | 
+----+--------------------+-------------------------------------+ 
+----+--------------------+------------------+------------------+ 
| id | title    | category   | content   | 
+----+--------------------+------------------+------------------+ 
| 1 | title1    | 1    | test1   | 
| 2 | title2    | 1    | test2   | 
| 3 | title3    | 2    | test3   | 
| 4 | title4    | 3    | test4   | 
| 5 | title5    | 1    | test5   | 
| 6 | title6    | 3    | test6   | 
| 7 | title7    | 4    | test7   | 
| 8 | title8    | 5    | test8   | 
| 9 | title9    | 5    | test9   | 
| 10 | title10   | 4    | test10   | 
| 11 | title11   | 6    | test11   | 
+----+--------------------+------------------+------------------+ 

嗨Select查詢，

假設父列0表示「這是一個主要的類別」類別表，其他爲其他類別的子類別。我想選擇cat1和cat1的子類別的所有內容。

Answer 1

檢查該查詢

select * from content_table where category IN (select id from category_table where parent IN 
(select id from category_table where cat_title = 'cat1'))