是否可以通过某些 IF 条件为 PostgreSQL 使用 WHERE？

Question

我有以下 SQL 报告请求。

select customers."AppId", second_dep "SecondDeps", first_dep "FirstDeps",
       customers_count "Customers", registrations "Registrations"
From (select Count("AppId") as customers_count, "AppId"
      FROM "Customers"
               join "Advertisers" A on "Customers"."AdvertiserId" = A."AdvertiserId"
               join "Categories" C2 on "Customers"."CategoryId" = C2."CategoryId"

      where A."Name" in (:AdvertiserNames)
        AND C2."Name" = :CategoryName
      GROUP BY "AppId"
     ) as customers

         left join

     (select C."AppId", count(CE.*) as second_dep
      from "CustomerEvents" as CE
               inner join "Customers" C on CE."CustomerId" = C."CustomerId"
      WHERE "EventType" = 'deposit'
        and "Again" = TRUE
      GROUP BY C."AppId") as dep2 on customers."AppId" = dep2."AppId"

        left  join

     (select C."AppId", count(CE.*) as first_dep
      from "CustomerEvents" as CE
               inner join "Customers" C on CE."CustomerId" = C."CustomerId"
      WHERE "EventType" = 'deposit'
        and "Again" = false
      GROUP BY C."AppId") as dep on customers."AppId" = dep."AppId"

         left join

     (select C."AppId", count(CE.*) as registrations
      from "CustomerEvents" as CE
               inner join "Customers" C on CE."CustomerId" = C."CustomerId"
      WHERE "EventType" = 'registration'
      GROUP BY C."AppId") as regs on regs."AppId" = customers."AppId";

有问题的字符串是

where A."Name" in (:AdvertiserNames)

如果AdvertiserNames为空，我想跳过它。可能吗？好的，我可以在代码方面检查它，但这种方式会导致我复制整个请求，但有一些小的差异（我的意思是如果 AdvertiserNames 为空运行 SQL 没有 where A."Name" in (:AdvertiserNames)).或者我可以使用串联来获得合适的 SQL。我也不喜欢这种方式。

关于我的技术栈。它是带有 PostgreSQL 的 .NET Core 2.2。这是整个报告方法的代码：

public IQueryable<ByApplicationsReportModel> ByApplications(string category, List<string> advertisers)
{
    var rawSql = new RawSqlString(@"
        select customers.""AppId"", second_dep ""SecondDeps"", first_dep ""FirstDeps"",
    customers_count ""Customers"", registrations ""Registrations""
            From (select Count(""AppId"") as customers_count, ""AppId""
            FROM ""Customers""
            join ""Advertisers"" A on ""Customers"".""AdvertiserId"" = A.""AdvertiserId""
            join ""Categories"" C2 on ""Customers"".""CategoryId"" = C2.""CategoryId""
            where A.""Name"" in (@AdvertiserNames)
            AND C2.""Name"" = @CategoryName
            GROUP BY ""AppId""
                ) as customers

                left join

                (select C.""AppId"", count(CE.*) as second_dep
                from ""CustomerEvents"" as CE
            inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
            WHERE ""EventType"" = 'deposit'
            and ""Again"" = TRUE
            GROUP BY C.""AppId"") as dep2 on customers.""AppId"" = dep2.""AppId""

            left  join

                (select C.""AppId"", count(CE.*) as first_dep
                from ""CustomerEvents"" as CE
            inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
            WHERE ""EventType"" = 'deposit'
            and ""Again"" = false
            GROUP BY C.""AppId"") as dep on customers.""AppId"" = dep.""AppId""

            left join

                (select C.""AppId"", count(CE.*) as registrations
                from ""CustomerEvents"" as CE
            inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
            WHERE ""EventType"" = 'registration'
            GROUP BY C.""AppId"") as regs on regs.""AppId"" = customers.""AppId""");

    var advertisersParam = new NpgsqlParameter("AdvertiserNames",  
        string.Join(",", advertisers) );

    var categoryParam = new NpgsqlParameter("CategoryName", category);

    return _context.ByApplicationsReportModels
        .FromSql(rawSql, categoryParam, advertisersParam);
}

有什么想法吗？

Answer 1

您可以尝试将 where A.""Name"" in (@AdvertiserNames) 更改为 where (A.""Name"" in (@AdvertiserNames) or @AdvertiserNames = '')。

Answer 2

您可以直接将字符串数组传递给您的查询，而不是将您的广告客户串联成一个字符串：

var advertisersParam = new NpgsqlParameter("AdvertiserNames", advertisers));

在 SQL 中，您需要更改为 x = ANY (@advertisers).

，而不是使用 x IN (@advertisers) 构造

注意：如果您希望在@advertisers 为空时通过检查，您仍然需要一个附加子句。

是否可以通过某些 IF 条件为 PostgreSQL 使用 WHERE？

Is it possible to use WHERE by some IF condition for PostgreSQL?

c#

postgresql

npgsql

.net-core