在android sqlite中选择不同的值
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select distinct value in android sqlite
提问by smith
I try to run the following raw query in android, it seems not work
我尝试在 android 中运行以下原始查询，它似乎不起作用
String query ="SELECT DISTINCT category FROM event";
Cursor cursor = mDb.rawQuery(query, null);
if (cursor != null) {
cursor.moveToFirst();
}
return cursor;
so I decide to use the query() method in android which are something like
所以我决定在 android 中使用 query() 方法，类似于
Cursor mCursor = mDb.query(EVENT_TABLE, new String[] {KEY_ROWID, KEY_CAT}, null, null,null,null, null)
Can anyone show me how to select the distinct category for using query() instead of rawquery please, any help will be greatly appreciated!
谁能告诉我如何选择使用 query() 而不是 rawquery 的不同类别，任何帮助将不胜感激！
回答by Adam Kowalski
But you MUST remember to send argument in GROUPBY(NOT NULLsend).
但是你必须记住在GROUPBY( NOT NULLsend) 中发送参数。
You must give column name for distinct.
您必须为distinct.
Example:
例子：
Cursor cursor = db.query(true, YOUR_TABLE_NAME, new String[] { COLUMN_NAME_1 ,COLUMN_NAME_2, COLUMN_NAME_3 }, null, null, COLUMN_NAME_2, null, null, null);
true - distinct TRUE
真 - 独特的真
COLUMN_NAME_2- name column what you have be DISTINCT.
COLUMN_NAME_2- 将列命名为 DISTINCT。
That's works for me fine.
这对我有用。
回答by Harry Joy
回答by Pavan Kunchapu
There are multiple ways, as already green ticked. But if somebody is looking to get it via raw query then here you go:
有多种方式，因为已经绿色打勾。但是，如果有人希望通过原始查询获取它，那么您就可以：
String query = "SELECT DISTINCT(category) FROM event";
回答by Ngosagoogle
Cursor res=db.rawQuery("select column1 column2... Distinct column3 from "+Table_name, null);
column3is a distinct column
column3是一个不同的列
