#inner join等值連接／內連接

mysql> select * from info; +------+-------------+----------+ | name | phone | address | +------+-------------+----------+ | zhao | 13199999999 | Beijing | | qian | 1328888888 | Harbin | | sun | 13366666666 | Shanghai | +------+-------------+----------+ 3 rows in set (0.00 sec) mysql> select * from score; +----+------+-------+------------+ | id | name | score | evaluation | +----+------+-------+------------+ | 1 | zhao | 98.00 | 10 | | 2 | qian | 90.30 | 10 | | 3 | sun | 70.00 | 10 | | 4 | li | 80.50 | 10 | +----+------+-------+------------+ 4 rows in set (0.00 sec)

#inner join——按照相同的name值（篩選行）連接兩個表中的某些字段（篩選列）構成表

mysql> select score.id,score.name,info.phone from score inner join info on score.name=info.name; +----+------+-------------+ | id | name | phone | +----+------+-------------+ | 1 | zhao | 13199999999 | | 2 | qian | 1328888888 | | 3 | sun | 13366666666 | +----+------+-------------+ 3 rows in set (0.00 sec)

#left join——讀取左邊表score的字段的所有值，按照相同的name值連接兩個表中的字段構成表（右邊的表沒有對應記錄的填null）

mysql> select score.id,score.name,info.phone from score left join info on score.name=info.name; +----+------+-------------+ | id | name | phone | +----+------+-------------+ | 1 | zhao | 13199999999 | | 2 | qian | 1328888888 | | 3 | sun | 13366666666 | | 4 | li | NULL | +----+------+-------------+ 4 rows in set (0.00 sec)

#類似的有right join

mysql> select score.id,score.name,info.phone from score right join info on score.name=info.name; +------+------+-------------+ | id | name | phone | +------+------+-------------+ | 1 | zhao | 13199999999 | | 2 | qian | 1328888888 | | 3 | sun | 13366666666 | +------+------+-------------+ 3 rows in set (0.00 sec)

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轉載于:https://www.cnblogs.com/IcarusYu/p/7497532.html

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