sql-server - 无法在 SQL Server 2019 中使用 Java Double.MIN_VALUE 4.9E-324 作为浮点文字

Question

使用 SQL Server 运行以下 JDBC 代码:

try (PreparedStatement s = connection.prepareStatement("select 4.9E-324, ?")) {
    s.setDouble(1, 4.9E-324);

    try (ResultSet rs = s.executeQuery()) {
        while (rs.next()) {
            System.out.println(rs.getDouble(1));
            System.out.println(rs.getDouble(2));
        }
    }
}

结果是:

0.0
4.9E-324

因此，虽然绑定(bind)值被正确回显，但文字却不是。这怎么解释？ I've noticed in the docs .

Any float value less than 5E-18 (when set using either the scientific notation of 5E-18 or the decimal notation of 0.0000000000000000050000000000000005) rounds down to 0. This is no longer a restriction as of SQL Server 2016 (13.x).

但我使用的是 SQL Server 2019

select @@version

产量:

Microsoft SQL Server 2019 (RTM-CU8-GDR) (KB4583459) - 15.0.4083.2 (X64) 
Nov  2 2020 18:35:09 
Copyright (C) 2019 Microsoft Corporation
Express Edition (64-bit) on Linux (Ubuntu 18.04.5 LTS) <X64>

以及最新版本的 SQL Server 的 JDBC 驱动程序

<dependency>
  <groupId>com.microsoft.sqlserver</groupId>
  <artifactId>mssql-jdbc</artifactId>
  <version>9.2.1.jre8</version>
</dependency>

Answer 1

那same documentation page还列出了有效浮点值的范围为:

-1.79E+308 to -2.23E-308, 0 and 2.23E-308 to 1.79E+308

所以，Java Double.MIN_VALUE超出范围。这有效:

try (PreparedStatement s = connection.prepareStatement("select 2.23E-308, ?")) {
    s.setDouble(1, 2.23E-308);

    try (ResultSet rs = s.executeQuery()) {
        while (rs.next()) {
            System.out.println(rs.getDouble(1));
            System.out.println(rs.getDouble(2));
        }
    }
}

生产:

2.23E-308
2.23E-308

但是，它没有解释为什么绑定(bind)变量被正确回显。