如何形成这个MYSQL查询

Question

我有下表

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" android:padding="5dp"> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@drawable/corner_shape" android:orientation="vertical"> <TextView android:id="@+id/tvCaption" android:layout_width="match_parent" android:layout_height="50dp" android:layout_marginBottom="-5dp" android:background="@drawable/upper_corner" android:gravity="center" android:text="@string/heading_order_reroute_page_title" android:textColor="@android:color/white" android:textSize="@dimen/heading_text_size" android:textStyle="bold" /> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@drawable/rectangle" android:gravity="center_vertical" android:orientation="horizontal" > <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="10dp" android:layout_weight="1" android:orientation="horizontal"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="center_vertical" android:text="@string/label_current_destination" android:textSize="@dimen/caption_text_size"/> <ImageView android:layout_width="0dp" android:layout_height="match_parent" android:layout_marginStart="5dp" android:layout_weight="0.1" android:contentDescription="@drawable/star" android:src="@drawable/star" android:visibility="invisible"/> </LinearLayout> <LinearLayout android:layout_width="0dp" android:layout_weight="2" android:orientation="vertical" android:layout_height="wrap_content"> <TextView android:id="@+id/tvCurrentDestination" android:layout_width="match_parent" android:layout_height="40dp" android:layout_margin="5dp" android:layout_weight="3" android:focusable="false" android:gravity="start|center_vertical" android:paddingStart="10dp" android:textSize="@dimen/caption_text_size"/> </LinearLayout> </LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@drawable/rectangle" android:gravity="center_vertical" android:orientation="horizontal" > <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="10dp" android:layout_weight="1" android:orientation="horizontal"> <TextView android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="0.9" android:gravity="center_vertical" android:text="@string/label_new_destination" android:textSize="@dimen/caption_text_size" /> <ImageView android:layout_width="0dp" android:layout_height="match_parent" android:layout_marginStart="5dp" android:layout_weight="0.1" android:contentDescription="@drawable/star" android:src="@drawable/star" /> </LinearLayout> <LinearLayout android:layout_width="0dp" android:layout_weight="2" android:orientation="vertical" android:layout_height="wrap_content"> <Spinner android:id="@+id/spinDestination" style="@android:style/Widget.Spinner" android:layout_width="match_parent" android:layout_height="40dp" android:layout_margin="5dp" android:dropDownHorizontalOffset = "?" android:dropDownVerticalOffset = "?" android:background="@drawable/bg_edit_text" android:gravity="start|center_vertical" android:paddingStart="10dp" android:spinnerMode="dropdown" /> </LinearLayout> </LinearLayout> <View android:layout_width="match_parent" android:layout_height="1dp" android:background="@color/divider_color" /> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@drawable/rectangle" android:gravity="center_vertical" android:orientation="horizontal" > <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="10dp" android:layout_weight="1" android:orientation="horizontal"> <TextView android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="0.9" android:gravity="center_vertical" android:text="@string/label_reroute_notes" android:textSize="@dimen/caption_text_size" /> <ImageView android:layout_width="0dp" android:layout_height="match_parent" android:layout_marginStart="5dp" android:layout_weight="0.1" android:contentDescription="@drawable/star" android:src="@drawable/star" /> </LinearLayout> <LinearLayout android:layout_width="0dp" android:layout_weight="2" android:orientation="vertical" android:layout_height="wrap_content"> <EditText android:id="@+id/etRerouteNotes" android:layout_width="match_parent" android:layout_height="120dp" android:layout_margin="5dp" android:background="@drawable/bg_edit_text" android:gravity="top|start" android:paddingStart="10dp" android:inputType="textMultiLine" android:scrollbars="vertical" android:fadeScrollbars="false" android:textSize="@dimen/edit_text_size" /> </LinearLayout> </LinearLayout> <View android:layout_width="match_parent" android:layout_height="1dp" android:background="@color/divider_color" /> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <Button android:id="@+id/btnReroute" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginBottom="10dp" android:layout_marginLeft="5dp" android:layout_marginRight="5dp" android:layout_marginTop="10dp" android:layout_weight="1" android:background="@drawable/btn_forward" android:gravity="center" android:paddingBottom="10dp" android:paddingTop="10dp" android:text="@string/btn_complete_order_reroute_caption" android:textColor="@android:color/white" android:textSize="@dimen/button_text_size" android:textStyle="bold" /> <Button android:id="@+id/btnCancel" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginBottom="10dp" android:layout_marginLeft="5dp" android:layout_marginRight="5dp" android:layout_marginTop="10dp" android:layout_weight="1" android:background="@drawable/btn_reject" android:gravity="center" android:paddingBottom="10dp" android:paddingTop="10dp" android:text="@string/btn_cancel_caption" android:textColor="@android:color/white" android:textSize="@dimen/button_text_size" android:textStyle="bold" /> </LinearLayout> </LinearLayout> </LinearLayout>

TABLE store

我想从每个不同的商店返回4级的数量 我知道我可以

store   name   level
1       Tom    4
2       Joe    2
1       Chris  4
3       Tom    2
4       Ed     2
2       Tom    4
3       Chris  2

要获得独特的商店和

select distinct store from store;

获取4级的计数

如何结合起来以在每个不同的商店中返回4级数量的查询 所以上面的数据会返回

select count(*) as level from store where level = 4;

Answer 1

不清楚为什么您的表被称为store。您不应该有一个名字每个商店只有一行的表吗？

在任何情况下，获取0计数的最简单方法可能是条件聚合：

select store, sum(level = 4) as level4
from store
group by store;