实时计算的join和传统批处理join的语义一致，都用于两张表之间的的join(例如，table a join table b)。不同的是实时计算的table a和table b是两张动态表，join的结果也会动态更新以保证最终结果和批处理的一致性。
语法
tableReference [, tableReference ]* | tableexpression[ LEFT ] JOIN tableexpression [ joinCondition ];
说明：
- 只支持等值连接, 不支持不等连接。
- 只支持inner join和left outer join两种
注意：DDL声明的字段、主键等要和真实表里面定义的一致。
示例一
测试语句
SELECT o.rowtime, o.productId, o.orderId, o.units, p.name, p.unitPrice FROM Orders AS o JOIN Products AS p ON o.productId = p.productId;
查询结果
| rowtime |
productId |
orderId |
units |
name |
unitPrice |
| 10:17:00 |
30 |
5 |
4 |
Cheese |
17 |
| 10:17:05 |
10 |
6 |
1 |
Beer |
0.25 |
| 10:18:05 |
20 |
7 |
2 |
Wine |
6 |
| 10:18:07 |
30 |
8 |
20 |
Cheese |
17 |
| 11:02:00 |
10 |
9 |
6 |
Beer |
0.25 |
| 11:04:00 |
10 |
10 |
1 |
Beer |
0.25 |
| 11:09:30 |
40 |
11 |
12 |
Bread |
100 |
| 11:24:11 |
10 |
12 |
4 |
Beer |
0.25 |
示例二
测试数据
datahub_stream1：
| a(bigint) |
b(bigint) |
c(VARCHAR) |
| 0 |
10 |
test11 |
| 1 |
10 |
test21 |
datahub_stream2：
| a(bigint) |
b(bigint) |
c(VARCHAR) |
| 0 |
10 |
test11 |
| 1 |
10 |
test21 |
| 0 |
10 |
test31 |
| 1 |
10 |
test41 |
测试语句
create table datahub_stream1 ( a int, b int, c varchar) WITH ( type='datahub', endpoint='', accessId='', accessKey='', projectName='', topic='', project='');create table datahub_stream2 ( a int, b int, c varchar) WITH ( type='datahub', endpoint='', accessId='', accessKey='', projectName='', topic='', project='');create table rds_output( s1_c varchar, s2_c varchar)with( type='rds', url='jdbc:mysql://XXXXXXX3306/test', tableName='udf', userName='tXXXXt', password='XXXX6');insert into rds_outputselect s1.c,s2.c from datahub_stream1 AS s1join datahub_stream2 AS s2 on s1.a =s2.awhere s1.a = 0;
测试结果
| s1_c(varchar) |
s2_c(varchar) |
| test1 |
test11 |
| test1 |
test31 |
