SQL 字段为字符型如'P12345678.X01',字段位数有11位和12位,用case wh...答:SELECT case when substring(QQ,1,1)='.' then '错误'when substring(QQ,2,1)='.' then substring(QQ,1,1)when substring(QQ,3,1)='.' then substring(QQ,1,2)when substring(QQ,4,1)='.' then substring(QQ,2,2)when substring(QQ,5,1)='.' then substring(QQ,3,2)when ...