Android 如何交换SQLite列中的值?
我有一个表(id,text),我需要交换如下列中的两个值:Android 如何交换SQLite列中的值?,android,sqlite,Android,Sqlite,我有一个表(id,text),我需要交换如下列中的两个值: Before. 1 one. 2 two. 3 three. After ( 1 and 3 swap) 1 three 2 two 3 one void updateMyTableText (MyTableRow row) { ContentValues values =
Before.
1 one.
2 two.
3 three.
After ( 1 and 3 swap)
1 three
2 two
3 one
void updateMyTableText (MyTableRow row)
{
ContentValues values = new ContentValues();
values.put ("text", MyTableRow.text);
String where = "id = ?";
String[] whereArgs = new String[1];
whereArgs[0] = Long.toString (row.id);
getDb().update ("MyTable", values, where, whereArgs);
}
要更新每一行,您需要如下内容:
Before.
1 one.
2 two.
3 three.
After ( 1 and 3 swap)
1 three
2 two
3 one
void updateMyTableText (MyTableRow row)
{
ContentValues values = new ContentValues();
values.put ("text", MyTableRow.text);
String where = "id = ?";
String[] whereArgs = new String[1];
whereArgs[0] = Long.toString (row.id);
getDb().update ("MyTable", values, where, whereArgs);
}
MyTableRow在哪里
class MyTableRow
{
long id;
String text;
}
您还需要一些查询来获取第1行和第3行的“文本”
以下是执行查询的一种方法:
long getId (String text)
{
// do the query
String query = "select id from MyTable where text = ? ";
String[] args = new String[1];
args[0] = text;
Cursor cursor = getDb().rawQuery (query, args);
if (cursor == null)
throw new IllegalStateException ("cursor is null");
try
{
// get the results
if (!cursor.moveToNext())
return -1; // row not found
long id = cursor.getLong (0);
return id;
}
finally
{
cursor.close();
}
}
您正在尝试更改行中的值吗?大多数数据库系统不允许您任意交换值,因为有一个假设,即它们是永久关联的。您可以发出UPDATE命令来永久修改这些值,但在返回数据后,暂时这样做可能会成为一个需要处理的问题
UPDATE table_name
SET text=three
WHERE id=1;
UPDATE table_name
SET text=one
WHERE id=3;
如果我有两个文本值,如何从db中检索id?很高兴听到它能工作。我还更新了示例,以演示如何执行查询。