{"id":9494,"date":"2021-01-25T16:22:16","date_gmt":"2021-01-25T07:22:16","guid":{"rendered":"https:\/\/www.gigas-jp.com\/appnews\/?p=9494"},"modified":"2021-01-22T20:02:42","modified_gmt":"2021-01-22T11:02:42","slug":"sql-joins","status":"publish","type":"post","link":"https:\/\/www.gigas-jp.com\/appnews\/archives\/9494","title":{"rendered":"SQL Joins"},"content":{"rendered":"\n

Today I would like to talk about MySQL joins along with some practical example queries.<\/p>\n\n\n\n

Inner Join<\/h3>\n\n\n\n

\uff12\u30c6\u30fc\u30d6\u30eb\u306e\u4e2d\u3067\u540c\u3058\u30ec\u30b3\u30fc\u30c9\u3060\u3051\u51fa\u308b\u3002
(return only matching records from both tables)<\/p>\n\n\n\n

Left Join<\/h3>\n\n\n\n

left \u30c6\u30fc\u30d6\u30eb\u306f\u5168\u30ec\u30b3\u30fc\u30c9\u304c\u51fa\u308b\u3001right \u30c6\u30fc\u30d6\u30eb\u306e\u306f\u540c\u3058\u30ec\u30b3\u30fc\u30c9\u3060\u3051
(return all records from the left table, and only the matched records from the right table)<\/p>\n\n\n\n

Right Join<\/h3>\n\n\n\n

right \u30c6\u30fc\u30d6\u30eb\u306f\u5168\u30ec\u30b3\u30fc\u30c9\u304c\u51fa\u308b\u3001left\u30c6\u30fc\u30d6\u30eb\u306e\u306f\u540c\u3058\u30ec\u30b3\u30fc\u30c9\u3060\u3051
(return all records from the right table, and only the matched records from the left table)<\/p>\n\n\n\n

Full Outer Join<\/h3>\n\n\n\n

\u540c\u3058\u30ec\u30b3\u30fc\u30c9\u304c\u6709\u308b\u6642\u5168\u90e8\u30ec\u30b3\u30fc\u30c9\u304c\u51fa\u308b\u3002
(return all records from both tables if there is match record between them)<\/p>\n\n\n\n

Inner Join Query Example<\/h3>\n\n\n\n

SELECT column(s)
FROM tb1
INNER JOIN tb2
ON tb1.column = tb2.column;<\/p>\n\n\n\n

Left Join Query Example<\/h3>\n\n\n\n

SELECT column(s)
FROM tb1
LEFT JOIN tb2
ON tb1.column = tb2.column;<\/p>\n\n\n\n

Right Join Query Example<\/h3>\n\n\n\n

SELECT column(s)
FROM tb1
RIGHT JOIN tb2
ON tb1.column = tb2.column;<\/p>\n\n\n\n

Full Outer Join Query Example<\/h3>\n\n\n\n

mysql doesn\u2019t support full join syntax directly so we can use this as an alternative.
(full join = left + right join)<\/em><\/p>\n\n\n\n

SELECT column(s)
FROM tb1
LEFT JOIN tb2 ON tb1.column = tb2.column;
LEFT JOIN tb3 ON tb1.column = tb3.column;
UNION
SELECT column(s)
FROM tb1
SELECT column(s)
FROM tb1
RIGHT JOIN tb2 ON tb1.column = tb2.column;
RIGHT JOIN tb3 ON tb1.column = tb3.column;<\/p>\n

\n
<\/g:plusone><\/div>\n
\"\u3053\u306e\u30a8\u30f3\u30c8\u30ea\u30fc\u3092\u306f\u3066\u306a\u30d6\u30c3\u30af\u30de\u30fc\u30af\u306b\u8ffd\u52a0\"<\/a>