结合两个表，并填写遗漏值在MySQL

Question

我有以下两个表中的MySQL：

表1：

ID Val1 
1 100 
2 200 
3 300 

表2：

ID Val2 
2 50 

我怎样才能结合他们成这样的桌子？

ID Val1 Val2 
1 100 0 
2 200 50 
3 300 0 

Answer 1

SELECT Table1.ID, Table1.Val1, COALESCE(Table2.Val2, 0) AS Val2 
FROM Table1 LEFT OUTER JOIN Table2 USING (ID) 

Answer 2

使用与IFNULL()结合一个LEFT JOIN在零来填补VAL2

SELECT 
    Table1.ID, 
    Table1.Val1, 
    IFNULL(Table2.Val2, 0) AS Val2 
FROM Table1 LEFT JOIN Table2 ON Table1.ID = Table2.ID 

Answer 3

SELECT Table1.ID, Table1.Val1, COALESCE(Table2.Val2, 0) AS Val2 
FROM Table1 LEFT OUTER JOIN Table2 USING (ID) 
INTO NewTable