DBRecordTable._ID
是一个INTEGER + PRIMARY_KEY+ AUTOINCREMENT
,我希望得到一个表的最大_id值,如果表中没有数据行将返回零.
我尝试编写代码 select(tableName,DBRecordTable._ID).orderBy(DBRecordTable._ID, Desc).limit(1)
,但它不正确,我该如何解决?
代码
class DBRecordHandler(private val mDBHelper: DBRecordHelper =DBRecordHelper.instance,
private val tableName:String =DBRecordTable.TableNAME,
private val idField:String=DBRecordTable._ID
) {
fun getMaxID():Long=mDBHelper.use{
var myList=select(tableName,DBRecordTable._ID).orderBy(DBRecordTable._ID, Desc).limit(1);
}
}
class DBRecordHelper(mContext: Context = UIApp.instance) : ManagedSQLiteOpenHelper(mContext, DB_NAME, null, DB_VERSION) {
companion object {
const val DB_NAME = "record.db"
const val DB_VERSION = 5
val instance by lazy { DBRecordHelper() }
}
override fun onCreate(db: SQLiteDatabase) {
db.createTable( DBRecordTable.TableNAME , true,
DBRecordTable._ID to INTEGER + PRIMARY_KEY+ AUTOINCREMENT,
DBRecordTable.CreatedDate to INTEGER
)
}
}
最佳答案
您可以使用 SQL
MAX()
函数找到表内容的最大 id:
private fun getMaxID(): Int {
var maxId = 0
mDBHelper?.use {
select(DBRecordTable.TableNAME, "MAX(${DBRecordTable._ID}) as maxId").exec {
moveToNext()
maxId = getInt(getColumnIndex("maxId"))
}
}
return maxId
}
关于android - 如何使用 Anko 和 Kotlin 获取 SQLite 表的最大 _id 值?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53357438/