查询中涉及到sum()函数和substr函数组合

sum( SUBSTR( xxx,3,1 ) = 5 OR SUBSTR( xxx,3,1 ) = 6 )  as sum,

运行后结果不正确，打印sql发现substr内参数被替换为：

sum( SUBSTR( xxx,1 ) = 5 OR SUBSTR( xxx,1 ) = 6 )  as sum,

解决办法，将substr中,分割使用表述语法代替：

sum( SUBSTR( xxx FROM 3 FOR 1 ) = 5 OR SUBSTR( xxx FROM 3 FOR 1 ) = 6 )  as sum,

再次运行，结果达到预期