我确信这句话在 Esper 中有效：
/* query from table TableA when receive event PriceEvent */
ON PriceEvent p
SELECT a.SymbolA, p.price
FROM TableA a
WHERE a.Symbol = p.Symbol
但是此语句会引发错误：
/* 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
错误信息：
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
错误信息：
Incorrect syntax near 'join' (a reserved keyword) expecting end-of-input but found 'join'
如何在 Esper 中连接两个表？