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TA贡献1775条经验 获得超8个赞
是否有任何特定需要在一个查询中执行此操作?因为虽然可以,但实际上使用原始解决方案并调用每个页面 ID 的查询可能更具可读性。无论如何,你想要的东西不能在一行中完成,所以你需要期望在给定的点循环。
// Build dynamic query
StringBuilder whereClause = new StringBuilder();
Iterator<PageID> it = yourMap.keySet().iterator();
while(it.hasNext()){
PageID key = it.next();
Set<SubscriberIDS> value = yourMap.get(key);
// You need to fill the 'IN' clause with multiple parameters, one for each subscriber id
StringBuilder inClause = new StringBuilder();
for(SubscriberIDS subId : value){
if(inClause.length > 0){
inClause.append(", ");
}
inClause.append("?");
preparedStatement.setInt(paramIndex++, subId.getId());
}
// For each page id we append a new 'OR' to our query
if(whereClause.lenght > 0){
whereClause.append(" OR ");
}
whereClause.append("(PAGEID=? AND SUBSCRIBERID IN (").append(inClause.toString()).append("))");
}
String query = "SELECT PAGEID, COUNT(SUBSCRIBERID) AS SUBSCRIBERS FROM FB_SUBSCRIPTIONS WHERE " + whereClause.toString() + " GROUP BY PAGEID";
// Create prepared statement and set parameters
PreparedStatement preparedStatement = connection.prepareStatement(query);
int paramIndex = 0;
it = yourMap.keySet().iterator();
while(it.hasNext()){
PageID key = it.next();
Set<SubscriberIDS> value = yourMap.get(key);
preparedStatement.setInt(paramIndex++, key.getId());
for(SubscriberIDS subId : value){
preparedStatement.setInt(paramIndex++, subId.getId());
}
}
// Execute query, loop over result and calculate new subscriptions
ResultSet rs = preparedStatement.executeQuery();
while(rs.next()){
int pageId = rs.getInt("PAGEID");
int newSubscriptions = yourMap.get(pageId).size() - rs.getInt("SUBSCRIBERS");
System.out.println(pageId + ", " + newSubscriptions);
}
在地图中给定以下数据:
PAGEID SUBSCRIBERIDS
1 1,3,4,5,9
2 3,4,5,6,8,9
3 2,5,6
以及数据库中的以下数据:
PAGEID SUBSCRIBERIDS
1 3,4,10,11
2 1,2,5,7
3 1,2,5,6,7,8,9
这应该给出以下输出:
1,3
2,6
3,0
我实际上还没有运行代码,所以它可能需要一些调整,但它给了你一般的想法......
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