SQL - 插入选择（多列）

Question

front end web guy thrown into the SQL abyss. Below is a prototype of our current SQL query:

 INSERT INTO table (table column)
 SELECT ad.val1, web.val2, ad.val3
 FROM ad
 LEFT JOIN web
 ON ad.val 4 = web.val4   

We've recently added a web.val5 column and we want to insert it's information to the same column as web.val4

I tried the following using the ALL clause:

 INSERT INTO table (table column)
 SELECT ad.val1, web.val2, ad.val3
 FROM ad
 LEFT JOIN web
 ON ad.val 4 = web.val4   
 AND ad.val4 = web.val5  

But I keep getting 0 (or NULL?). Is there a certain clause that I can add to a LEFT JOIN that can equate a value to two different values in different columns within the same table? Sorry if this is confusing, I barely understand it myself.

Answer 1

You can consider joining it twice and match that condition like

 INSERT INTO table (table column)
 SELECT ad.val1, web.val2, ad.val3
 FROM ad
 LEFT JOIN web
 ON ad.val4 = web.val4  
 LEFT JOIN web w           //second join
 ON ad.val4 = w.val5