Android Sqlite 检查表是否为空
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Sqlite Check if Table is Empty
提问by mehmet
Well, I have a databse and it has lots of table. but generally tables are empty. I want check if a database table is empty. IF table is empty, program will fill it.
好吧，我有一个数据库，它有很多表。但通常表是空的。我想检查数据库表是否为空。如果表为空，程序将填充它。
public static long queryNumEntries (SQLiteDatabase db, String table)
I will use it but it requre API 11.
我会使用它，但它需要 API 11。
回答by Waqar Ahmed
you can execute select count(*) from tableand check if count> 0then leave else populate it.
您可以执行select count(*) from table并检查是否count> 0然后留下其他填充它。
like
喜欢
SQLiteDatabase db = table.getWritableDatabase();
String count = "SELECT count(*) FROM table";
Cursor mcursor = db.rawQuery(count, null);
mcursor.moveToFirst();
int icount = mcursor.getInt(0);
if(icount>0)
//leave
else
//populate table
回答by Luca Sepe
Do a SELECT COUNT:
做一个SELECT COUNT：
boolean empty = true
Cursor cur = db.rawQuery("SELECT COUNT(*) FROM YOURTABLE", null);
if (cur != null && cur.moveToFirst()) {
empty = (cur.getInt (0) == 0);
}
cur.close();
return empty;
回答by Dwivedi Ji
Optimal Solutions
最佳解决方案
public boolean isMasterEmpty() {
boolean flag;
String quString = "select exists(select 1 from " + TABLE_MASTERS + ");";
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery(quString, null);
cursor.moveToFirst();
int count= cursor.getInt(0);
if (count ==1) {
flag = false;
} else {
flag = true;
}
cursor.close();
db.close();
return flag;
}
回答by Mahesh Uligade
public boolean isEmpty(String TableName){
SQLiteDatabase database = this.getReadableDatabase();
int NoOfRows = (int) DatabaseUtils.queryNumEntries(database,TableName);
if (NoOfRows == 0){
return true;
}else {
return false;
}
}
回答by Juan Pablo Arango
Here is a better option:
这是一个更好的选择：
public boolean validateIfTableHasData(SQLiteDatabase myDatabase,String tableName){
Cursor c = myDatabase.rawQuery("SELECT * FROM " + tableName,null);
return c.moveToFirst();
}
回答by My God
This is how you can do it-
这就是你可以做到的-
if(checkTable("TABLE"))
{
//table exists fill data.
}
Method to check table-
查表方法——
public static boolean checkTable(String table) {
Cursor cur2 = dbAdapter.rawQuery("select name from sqlite_master where name='"
+ table + "'", null);
if (cur2.getCount() != 0) {
if (!cur2.isClosed())
cur2.close();
return true;
} else {
if (!cur2.isClosed())
cur2.close();
return false;
}
}
回答by Денис Климков
I think, this solution is better:
我认为，这个解决方案更好：
boolean flag;
DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext(), DatabaseHelper.DATABASE_NAME, null, DatabaseHelper.DATABASE_VERSION);
try {
sqLiteDatabase = databaseHelper.getWritableDatabase();
} catch (SQLException ex) {
sqLiteDatabase = databaseHelper.getReadableDatabase();
}
String count = "SELECT * FROM table";
Cursor cursor = sqLiteDatabase.rawQuery(count, null);
if (cursor.moveToFirst()){
flag = false;
} else {
flag = true;
}
cursor.close();
sqLiteDatabase.close();
return flag;
moveToFirst()check table and return true, if table is empty. Answer that is marked correct - uses extra check.
moveToFirst()检查表并返回true，如果表为空。标记为正确的答案 - 使用额外检查。
