java - 为什么我的 SELECT COUNT 查询不起作用？

Question

//creating a resultset + connecting with the connection method and typing in query
ResultSet rowCount = MainApp.dataBaseSelect("SELECT COUNT(isFoundStatus) FROM damageclaim");

//creating int variable but needs a value since in later row it says ' might not be initalized '
int rowCountInt = 0;

//giving the resultset to the int.
while (rowCount.next()){
    rowCountInt = rowCount.getInt("isFoundStatus");
}
//testing with system out
System.out.println(rowCountInt);

我希望获取数据库行的长度，但由于某种原因它不起作用，而数据库的其他连接却可以工作。

我得到的错误:找不到该列，即使我确实拥有它......

Answer 1

让我们假设您正在使用 JDBC。在这种情况下，您需要执行以下两件事之一:

1. 给您的列起别名，以便您可以按名称引用它:

   select count(isFoundStatus) as total from damageclaim;
   // later on
   rowCountInt = rowCount.getInt("total");
   

2. 使用列索引来获取第一个值:

   select count(isFoundStatus) from damageclaim;
   // later on
   rowCountInt = rowCount.getInt(1);