如何将一个字段中的日期与另一个字段中的时间结合起来 - MS SQL Server [英] How to combine date from one field with time from another field - MS SQL Server

问题描述

在我正在处理的摘录中，我有 2 个 datetime 列.如图所示，一列存储日期，另一列存储时间.

如何查询表格以将这两个字段合并为 1 列类型为 datetime?

日期

2009-03-12 00:00:00.0002009-03-26 00:00:00.0002009-03-26 00:00:00.000

时代

1899-12-30 12:30:00.0001899-12-30 10:00:00.0001899-12-30 10:00:00.000

解决方案

两者相加即可.

• 如果 Date 列的Time 部分 始终为零
• 并且您的 Time 列的 Date 部分 也始终为零(基准日期:1900 年 1 月 1 日)

添加它们会返回正确的结果.

SELECT Combined = MyDate + MyTime FROM MyTable

基本原理(感谢 ErikE/dnolan)

<块引用>

由于日期存储为两个 4 字节的方式，它的工作原理是这样的Integers，左边 4 字节是 date，右边4 字节是 time.就像在做 $0001 0000 + $0000 0001 =$0001 0001

关于新的 SQL Server 2008 类型的编辑

Date 和 Time 是 SQL Server 2008 中引入的类型.如果你坚持添加，可以使用 Combined = CAST(MyDate AS DATETIME) + CAST(MyTime AS DATETIME)

Edit2 关于 SQL Server 2008 及更高版本中的精度损失(感谢 Martin Smith)

看看 如何要在 SQL Server 中将日期和时间组合到 datetime2? 以防止在使用 SQL Server 2008 及更高版本时丢失精度.

In an extract I am dealing with, I have 2 datetime columns. One column stores the dates and another the times as shown.

How can I query the table to combine these two fields into 1 column of type datetime?

Dates

2009-03-12 00:00:00.000
2009-03-26 00:00:00.000
2009-03-26 00:00:00.000

Times

1899-12-30 12:30:00.000
1899-12-30 10:00:00.000
1899-12-30 10:00:00.000

解决方案

You can simply add the two.

• if the Time part of your Date column is always zero
• and the Date part of your Time column is also always zero (base date: January 1, 1900)

Adding them returns the correct result.

SELECT Combined = MyDate + MyTime FROM MyTable

Rationale (kudos to ErikE/dnolan)

It works like this due to the way the date is stored as two 4-byte Integers with the left 4-bytes being the date and the right 4-bytes being the time. Its like doing $0001 0000 + $0000 0001 = $0001 0001

Edit regarding new SQL Server 2008 types

Date and Time are types introduced in SQL Server 2008. If you insist on adding, you can use Combined = CAST(MyDate AS DATETIME) + CAST(MyTime AS DATETIME)

Edit2 regarding loss of precision in SQL Server 2008 and up (kudos to Martin Smith)

Have a look at How to combine date and time to datetime2 in SQL Server? to prevent loss of precision using SQL Server 2008 and up.

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