java 如何在sqlite select语句中设置2个小数位
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How to set 2 decimal places in sqlite select statement
提问by SAN
I have a sqlite table that has amount field with NUMERIC(10,5) value(I know data type meant not much in sqlite). I want to write a select statement that display amount in 2 decimal places.
我有一个带有 NUMERIC(10,5) 值的数量字段的 sqlite 表（我知道数据类型在 sqlite 中意义不大）。我想写一个选择语句，以 2 个小数位显示金额。
id name type notnull dflt_value pk
------- --------------- ---------- ----------- -------------- ---
0 _id integer 0 1
1 name varchar 1 0
2 amount NUMERIC(10,5) 0 0
SELECT _id, name, amount FROM accounts
Is it possible to convert the amount in two decimal places within the select statement, so I can display with two decimal places in the application. I need to format in the select statement, don't wants to change the table structure. Thanks in advance.
是否可以在 select 语句中将金额转换为两位小数，以便我可以在应用程序中显示两位小数。我需要在select语句中格式化，不想改变表结构。提前致谢。
Im using following code to populate the the list view in android
我使用以下代码填充 android 中的列表视图
cursor = dbAdapter.getAccountsTotals();
startManagingCursor(cursor);
String[] from = new String[] { DbAdapter.KEY_ID, DbAdapter.KEY_NAME, DbAdapter.KEY_AMOUNT};
int[] to = new int[] { R.id.dis1, R.id.dis2, R.id.dis3};
SimpleCursorAdapter trans = new SimpleCursorAdapter(this, R.layout.accts_row, cursor, from, to);
setListAdapter(trans);
so can not format the results after fetching form the database. Please let me know it there is a way to assign formatted values in above code, thanks.
所以无法在从数据库中获取后格式化结果。请让我知道有一种方法可以在上面的代码中分配格式化的值，谢谢。
回答by Rupok
SELECT _id, name, ROUND(amount,2) FROM accounts
Following code will give you idea how you can do it
以下代码将让您了解如何做到这一点
public class TestListView extends ListActivity {
...
private DecimalFormat myCustDecFormatter = new DecimalFormat("########.00");
...
...
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
...
...
...
}
private void fillData() {
/* Get all of the rows from the database and create the item list */
/* for mult accts, pass in acct name? */
mEntryCursor = mDbHelper.fetchAllEntries();
startManagingCursor(mEntryCursor);
// Create an array to specify the fields we want to display in the list (only TITLE)
String[] from = new String[]{myDbAdapter.KEY_NMBR,myDbAdapter.KEY_DATE,myDbAdapter.KEY_DESCR,myDbAdapter.KEY_AMT};
// and an array of the fields we want to bind those fields to (in this case just text1)
int[] to = new int[]{R.id.txtnmbr, R.id.txtdate, R.id.txtdescr, R.id.txtamt};
// Now create a simple cursor adapter and set it to display
setListAdapter(new SimpleCursorAdapter(this, R.layout.entryrow, mEntryCursor, from, to) {
@Override
public void setViewText(TextView v, String text) {
super.setViewText(v, convText(v, text));
}
});
}
private String convText(TextView v, String text) {
switch (v.getId()) {
case R.id.txtamt:
double dblAmt;
//dblAmt = Double.valueOf(text);
dblAmt = mEntryCursor.getDouble(AMT_COLUMN);
return myCustDecFormatter.format(dblAmt);
}
return text;
}
}//end TestListView
回答by Kennet
Leave float value as it is in the database and format in presentation layer, somthing like this:
将浮点值保留在数据库中，并在表示层中设置格式，如下所示：
float f = 1.23456f;
NumberFormat instance = NumberFormat.getInstance();
instance.setMaximumFractionDigits(2);
System.out.println(instance.format(f));
