sparksql--join关联执行情况

最新推荐文章于 2024-11-18 21:23:27 发布

好好好你说的都对

最新推荐文章于 2024-11-18 21:23:27 发布

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分类专栏： sparksql sql 文章标签： join left join inner join

本文链接：https://blog.youkuaiyun.com/sinat_36755318/article/details/79877332

本文通过实例探讨了SparkSQL中join操作的不同类型，包括left join、inner join的组合使用，分析了不同join顺序对结果的影响，并展示了执行计划的关键部分。

准备5张表的数据，例如

select * from yxl_test;
+----+-------+-----+
| id | name | val |
+----+-------+-----+
| 3 | au | 90.0 |
| 6 | pp | 92.0 |
| 8 | we | 57.0 |
| 8 | we | 27.0 |
| 6 | | 85.0 |
| 3 | tom | 30.0 |
| 12 | | 78.0 |
| NULL| jay | 49.0 |
| 7 | jy | 28.0 |
| 9 | | NULL |

+-------+-------+-------+

cache table yxl_test1 as select id,name,val from yxl_test order by id limit 2;

select * from yxl_test1;
+-------+-------+-------+
| id | name | val |
+-------+-------+-------+
| NULL | jay | 49.0 |
| 3 | tom | 30.0 |

+-------+-------+-------+

cache table yxl_test2 as select id,name,val from yxl_test order by id desc limit 2;

select * from yxl_test2;
+-----+-------+-------+--+
| id | name | val |
+-----+-------+-------+--+
| 12 | | 78.0 |
| 9 | | NULL |

+-----+-------+-------+--+

cache table yxl_test3 as select id,name,val from yxl_test where id = 6;

select * from yxl_test3;
+-----+-------+-------+--+
| id | name | val |
+-----+-------+-------+--+
| 6 | pp | 92.0 |
| 6 | | 85.0 |

+-----+-------+-------+--+

cache table yxl_test4 as select id,name,val from yxl_test where id=3;

select * from yxl_test4;
+-----+-------+-------+--+
| id | name | val |
+-----+-------+-------+--+
| 3 | au | 90.0 |
| 3 | tom | 30.0 |