我有一个包含数据的表，需要通过两个字段进行连接。
我写了一个请求，但不起作用

SELECT * 
FROM Data t1 
JOIN Data t2 ON t1.s = t2.o

代码是

val csvTableSource = CsvTableSource
  .builder
  .path("src/main/resources/data.dat")
  .field("s", Types.STRING)
  .field("p", Types.STRING)
  .field("o", Types.STRING)
  .field("TIMESTAMP", Types.STRING)
  .fieldDelimiter(",")
  .ignoreFirstLine
  .ignoreParseErrors
  .commentPrefix("%")
  .build()
tableEnv.registerTableSource("Data", csvTableSource)

val query = "SELECT * FROM Data t1 JOIN Data t2 ON t1.s = t2.o"
val table = tableEnv.sqlQuery(query)

我得到以下例外

Exception in thread "main" org.apache.flink.table.api.TableException: Cannot generate a valid execution plan for the given query: 

FlinkLogicalJoin(condition=[=($0, $6)], joinType=[inner])
  FlinkLogicalTableSourceScan(table=[[Data]], fields=[s, p, o, TIMESTAMP], source=[CsvTableSource(read fields: s, p, o, TIMESTAMP)])
  FlinkLogicalTableSourceScan(table=[[Data]], fields=[s, p, o, TIMESTAMP], source=[CsvTableSource(read fields: s, p, o, TIMESTAMP)])

This exception indicates that the query uses an unsupported SQL feature.
Please check the documentation for the set of currently supported SQL features.