Esper如何连接表

Question

我确信这个语句在Esper中是有效的：

/* query from table TableA when receive event PriceEvent */
ON PriceEvent p
SELECT a.SymbolA, p.price
FROM TableA a
WHERE a.Symbol = p.Symbol

但是这条语句抛出了错误：

/* join table TableA with TableB */
ON PriceEvent p
SELECT a.SymbolA, p.price, b.SymbolB
FROM TableA a, TableB b
WHERE a.Key = b.Key and a.Symbol = p.Symbol

错误消息：

com.espertech.esper.client.EPStatementSyntaxException: Incorrect syntax near ',' expecting end-of-input but found a comma ','

然后我使用JOIN，但它仍然不起作用：

/* join table TableA with TableB */
ON PriceEvent p
SELECT a.SymbolA, p.price, b.SymbolB
FROM TableA a inner join TableB b
ON a.Key = b.Key
WHERE a.Symbol = p.Symbol

错误消息：

Incorrect syntax near 'join' (a reserved keyword) expecting end-of-input but found 'join'

如何在Esper中连接两个表？

Answer 1

on-select只允许一个命名窗口或表，而不允许多个。Joins只是"select * from A，B，C...“你可以考虑使用“单向”。