Question

我正在努力在我的android项目中结合几个sqlite查询。

我通过此次调用获得了ItemTable的所有元素

String sql = "SELECT n.*, p.ParentID "
           + "FROM NameTable n, "
           + "     ItemTable p "
           + "WHERE p.itemID = n.OwnerID "
           + "COLLATE NOCASE";

然后让他们的每个父母参与以下两个查询中的一个：

if (aItem.parentID > 0) {
    sql = "SELECT n.*, p.ParentID, f.FamilyID "
        + "FROM NameTable n, "
        + "     FamilyTable f, "
        + "     ItemTable p "
        + "WHERE f.FamilyID = '" + aItem.parentID + "' "
        + "  AND p.ItemID = n.OwnerID "
        + "  AND (p.ItemID = f.MotherID OR p.itemID = f.FatherID) "
        + "  AND n.IsPrimary = 1 ";
} else {
    sql = "SELECT n.*, p.ItemID, f.FamilyID "
        + "FROM NameTable n, "
        + "     FamilyTable f, "
        + "     ChildTable c, "
        + "     ItemTable p "
        + "WHERE c.ChildID = '" + aItem.ItemID + "' "
        + "  AND p.ItemID = n.OwnerID "
        + "  AND c.FamilyID = f.FamilyID "
        + "  AND (p.ItemID = f.MotherID OR p.ItemID = f.FatherID) "
        + "  AND n.IsPrimary = 1 ";
}

有什么方法可以将这三个查询和逻辑组合成一个？我认为组合调用会更快，但我不知道如何组合它们，并且如果我将它们组合起来也不确定如何读取行。我真的可以使用一些建议和帮助。

Answer 1

如果您不介意在一个结果集中同时获得两个查询的结果，可以通过在查询之间添加“UNION”，同时在列名称中添加“AS”并添加来联合2个查询。一个新列，用于区分每个查询的结果

sql = "SELECT n.*, p.ParentID AS ID1, f.FamilyID, 1 AS RESULT_GROUP "
    + "FROM NameTable n, "
    + "     FamilyTable f, "
    + "     ItemTable p "
    + "WHERE f.FamilyID = '" + aItem.parentID + "' "
    + "  AND p.ItemID = n.OwnerID "
    + "  AND (p.ItemID = f.MotherID OR p.itemID = f.FatherID) "
    + "  AND n.IsPrimary = 1 ";
sql += " UNION "
sql += "SELECT n.*, p.ItemID AS ID1, f.FamilyID AS ID2, 2 AS RESULT_GROUP "
    + "FROM NameTable n, "
    + "     FamilyTable f, "
    + "     ChildTable c, "
    + "     ItemTable p "
    + "WHERE c.ChildID = '" + aItem.ItemID + "' "
    + "  AND p.ItemID = n.OwnerID "
    + "  AND c.FamilyID = f.FamilyID "
    + "  AND (p.ItemID = f.MotherID OR p.ItemID = f.FatherID) "
    + "  AND n.IsPrimary = 1 ";

同样在你的联接上，我会做一些事情（改善表现）：

sql = "SELECT n.*, p.ParentID AS ID1, f.FamilyID, 1 AS RESULT_GROUP "
    + "FROM NameTable n "
    + "JOIN FamilyTable f ON f.FamilyID = '" + aItem.parentID + "' "
    + "JOIN ItemTable p ON p.ItemID = n.OwnerID"
    + "WHERE 
    + "  (p.ItemID = f.MotherID OR p.itemID = f.FatherID) "
    + "  AND n.IsPrimary = 1 ";

结合多个Sqlite查询

1 个答案: