Question

以下查询在MySQL提示符中正确执行但是在Java中出错（您的SQL语法有错误;请查看与您的MySQL服务器版本对应的手册，以便在'by附近使用正确的语法（选择avg时的案例等级，然后当'A'时为4，然后当'A'时为4 - '然后在第1行3.7 w'

java.sql.ResultSet rslt= stmt.executeQuery("select name from student natural join takes t1 where (dept_name='Comp. Sci.')" +
        "group by ID" +
        "order by (select avg( case grade " +
                        "when 'A+' then 4 " +
                        "when 'A' then 4 " +
                        "when 'A-' then 3.7 " +
                        "when 'B+' then 3.5 " +
                        "when 'B' then 3 " +
                        "when 'B-' then 2.7 " +
                        "when 'C+' then 2.5 " +
                        "when 'C' then 2 " +
                        "when 'C-' then 1 " +
                        "end) as avg_gpa " +
                   "from takes t2 " +
               "where t1.ID=t2.ID) " +
        "limit 10");

有人可以帮忙吗？

Answer 1

不要忘记每行后面的空格：

java.sql.ResultSet rslt= stmt.executeQuery(
"select name from student natural join takes t1 where (dept_name='Comp. Sci.') "+
"group by ID "+
"order by (select avg( case grade "+
        "when 'A+' then 4  "+
    "when 'A' then 4 "+
    "when 'A-' then 3.7 "+
    "when 'B+' then 3.5 "+
    "when 'B' then 3 "+
    "when 'B-' then 2.7 "+
    "when 'C+' then 2.5 "+
    "when 'C' then 2 "+
    "when 'C-' then 1 "+
    "end) as avg_gpa "+
    "from takes t2 "+
"where t1.ID=t2.ID) "+
"limit 10");

你的sql错了：

"group by ID" +
        "order by (select avg( case grade " +

这里有一个像这样的字符串："group by IDorder by (select avg( case grade"

你看到了问题吗？

在ID

之后添加空格

查询在MySQL提示符中执行，但不在应用程序中执

1 个答案: