前言

• full outer join结合了 LEFT JOIN 和 RIGHT JOIN 的结果，并使用NULL值作为两侧缺失匹配结果。

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语法 :

SELECT 
    table1.column_name(s),table2.column_name(s) 
FROM table1 
    FULL OUTER JOIN table2 
ON table1.column_name = table2.column_name;

• 相当于:left join + union + right join

SELECT 
    table1.column_name(s),table2.column_name(s)
FROM table1 
    LEFT OUTER JOIN table2 
ON table1.column_name = table2.column_name
UNION
SELECT 
    table1.column_name(s),table2.column_name(s)
FROM table1 
    RIGHT OUTER JOIN table2 
ON table1.column_name = table2.column_name;

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总结

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参考1